NCERT MCQ CLASS-12 CHAPTER-14 | CHEMISTRY NCERT MCQ | BIOMOLECULES | EDUGROWN

In This Post we are  providing Chapter-14 Biomolecules  NCERT MCQ for Class 12 Chemistry which will be beneficial for students. These solutions are updated according to 2021-22 syllabus. These MCQS  can be really helpful in the preparation of Board exams and will provide you with a brief knowledge of the chapter.

NCERT MCQ ON BIOMOLECULES

Question 1 : Which of the following gives positive Fehling solution test?

(a) Protein  (b) Sucrose
(c) Glucose (d) Fats

Answer : C

Question 2: Which of the following statements is incorrect regarding glucose?

(a) It is an aldohexose.
(b) It is also known as dextrose
(c) It is monomer of cellulose.
(d) It is the least abundant organic compound on earth.

Answer : D 

Question 3 : Glucose gives silver mirror test with Tollen’s reagent. It shows the presence of

(a) acidic group   (b) alcoholic group
(c) ketonic group (d) aldehyde group

Answer : D  

Question 4: The symbols D and L represents

(a) the optical activity of compounds.
(b) the relative configuration of a particular stereoisomer.
(c) the dextrorotatory nature of molecule.
(d) the levorotatory nature of molecule

Answer : B 

Question 5:   The function of glucose is to

(a) provides energy  (b) promote growth
(c) prevent diseases (d) perform all above

Answer : A

Question 6 : Which one of the following compounds is different from the rest?

(a) Sucrose (b) Maltose
(c) Lactose (d) Glucose

Answer : D 

Question 7 : The two functional groups present in a typical carbohydrate are:

(a) – CHO and – COOH   (b) > C = O and – OH
(c) – OH and – CHO       (d) – OH and – COOH

Answer : C 

Question 8: When glucose reacts with bromine water, the main product is

(a) gluconic acid   (b) glyceraldehyde
(c) saccharic acid (d) acetic acid

Answer : A 

Question 9: Glucose does not react with

(a) Br2/H2O (b) H2NOH
(c) HI         (d) NaHSO3

Answer : D 

Question 10: Biomolecules are

(a) aldehydes and ketones
(b) acids and esters
(c) carbohydrates, proteins and fats
(d) alcohols and phenols

Answer : C

Question 11 : Which of the following monosaccharide is pentose ?

(a) Glucose    (b) Fructose
(c) Arabinose (d) Galactose

Answer : C

Question 12: Which one of the following compounds is found abundantly in nature?

(a) Fructose (b) Starch
(c) Glucose  (d) Cellulose

Answer : D

Question 13: A carbohydrate that cannot be hydrolyzed into simpler units is called

(a) polysaccharides (b) trisaccharide
(c) disaccharides    (d) monosaccharides

Answer : D

Question 14 : Which of the following statements is incorrect ?

(a) Maltose gives two molecules of glucose only.
(b) Cellulose and sucrose are polysaccharide.
(c) Polysaccharides are not sweet in taste.
(d) Polysaccharides are also known as non-sugars

Answer : B

Question 15 : Reducing sugars reduce.

(a) only Fehling’s solution
(b) only Tollen’s solution.
(c) both (a) & (b)
(d) neither (a) nor (b)

Answer : C

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NCERT MCQ CLASS-12 CHAPTER-13 | CHEMISTRY NCERT MCQ | AMINES | EDUGROWN

In This Post we are  providing Chapter-13 Amines  NCERT MCQ for Class 12 Chemistry which will be beneficial for students. These solutions are updated according to 2021-22 syllabus. These MCQS  can be really helpful in the preparation of Board exams and will provide you with a brief knowledge of the chapter.

NCERT MCQ ON AMINES

Question 1.
Nitrogen atom of amino group is ………. hybridized.

(a) sp
(b) sp2
(c) sp3
(d) sp3d

Answer: (c) sp3

Question 2.
Which of the following should be most volatile?

I. CH3CH2CH2NH2
II. (CH3)3N
MCQ Questions for Class 12 Chemistry Chapter 13 Amines with Answers 1
IV. CH3CH2CH3
(a) II
(b) IV
(c) I
(d) III

Answer: (b) IV

Question 3.
C3H8N cannot represent

(a) 1° ammine
(b) 2° ammine
(c) 3° ammine
(d) quaternary ammonium salt

Answer: (d) quaternary ammonium salt

Question 4.
Identify the correct IUPAC name

(a) (CH3CH2)2NCH3 = N-Ethyl-N-methylethanamine
(b) (CH3)3CNH2 = 2-methylpropan-2-amine
(c) CH3NHCH (CH3)2 = N-Methylpropan-2-amine
(d) (CH3)2CHNH2 = 2, 2-Dimethyl-N-propanamine

Answer: (a) (CH3CH2)2NCH3 = N-Ethyl-N-methylethanamine

Question 5.
The most convenient method to prepare primary (i Amine) amine containing one carbon atom less is

(a) Gabriel phthalimide synthesis
(b) Reductive amination of aldehydes
(c) Hofmann bromamide reaction
(d) Reduction of isonitriles

Answer: (c) Hofmann bromamide reaction

Question 6.
Identify the correct pathway to convert propanoic acid to ethylamine. The reagent represented by A, B and C are

MCQ Questions for Class 12 Chemistry Chapter 13 Amines with Answers 2

Answer: (b)

Question 7.
When excess of ethyl iodide is treated with ammonia, the product is

(a) ethylamine
(b) dimethylamine
(c) triethylamine
(d) tetraethylammonium iodide

Answer: (d) tetraethylammonium iodide

Question 8.
Amides may be converted into amines by a reaction named after

(a) Hofmann Bromide
(b) Claisen
(c) Perkin
(d) Kerulen

Answer: (a) Hofmann Bromide

Question 9.
Reduction of CH3CH2NC with hydrogen in presence of Ni or Pt as
catalyst gives
(a) CH3CH2NH2
(b) CH3CH2NHCH3
(c) CH3CH2NHCH2CH3
(d) (CH3)3N

Answer: (b) CH3CH2NHCH3

Question 10.
Secondary amines can be prepared by

(a) reduction of nitro compounds
(b) oxidation of N-substituted amides
(c) reduction of isonitriles
(d) reduction of nitriles

Answer: (c) reduction of isonitriles

Question 11.
Which of the following amides will give ethylamine on reaction with sodium hypo bromide?

(a) Butanamide
(b) Propanamide
(c) Acetamide
(d)Benzamide

Answer: (b) Propanamide

Question 12.
Benzoic acid is treated with SOCl2 and the product (X) formed is reacted with ammonia to give (Y). (Y) on reaction with Br2 and KOH gives (Z). (Z) in the reaction is

(a) aniline
(b) chlorobenzene
(c) benzamide
(d) benzoyl chloride

Answer: (a) aniline

Question 13.
Which one of the following reducing agents is likely to be most effective in bringing about the following change?
MCQ Questions for Class 12 Chemistry Chapter 13 Amines with Answers 3

(a) H2-Ni
(b) NaBH4
(c) LiAlH4 ether
(d) Na-Alcohol

Answer: (c) LiAlH4 ether

Question 14.
Amine that cannot be prepared by Gabricl-Phthalmidie synthesis is

(a) aniline
(b) benzyl amine
(c) methyl amine
(d) iso-butylamine

Answer: (a) aniline

Question 15.
What is the end product in the following sequence of reactions?

MCQ Questions for Class 12 Chemistry Chapter 13 Amines with Answers 4
(a) Aniline
(b) Phenol
(c) Benzene
(d) Benzenediazxonium chloride

Answer: (a) Aniline




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NCERT MCQ CLASS-12 CHAPTER-12 | CHEMISTRY NCERT MCQ | ALDEHYDE, KETONES AND CARBOXYLIC ACIDS | EDUGROWN

In This Post we are  providing Chapter-12 Aldehyde, Ketones and Carboxylic acids  NCERT MCQ for Class 12 Chemistry which will be beneficial for students. These solutions are updated according to 2021-22 syllabus. These MCQS  can be really helpful in the preparation of Board exams and will provide you with a brief knowledge of the chapter.

NCERT MCQ ON ALDEHYDE, KETONES AND CARBOXYLIC ACIDS

1) Which of the following carbonyl compound is used in the preparation of ice cream

a) berzophenone

b) acetophenone

c) acetone

d) acetaldehyde

Answer- : b

2) The polar nature of carbonyl group in aldehydes and ketones is due to____________

a) very less electronegative difference

b) very large electronagative difference

c) presence ot hydrogen bonding

d) presence of sp hybridised characters in carbonyl compound

Answer- : b

3) Which of the following organic compounds are second oxidation products of alkanes?

a) 1°and 2° alcohols

b) carboxylic acids and esters

c) 2° and 3° alcohols

d) aldehyde and ketones

Answer- : d

4) phenones are_________

a) aldehyde in which carbonyl group is attached with benzene ring

b) ketone in which carbonyl group is attached with benzene ring

c) phenols in which carbonyl group is attached with alkyl group 

d) phenols in which carbonyl group is attached with group

Answer- : b

5) Mesity oxide is _________

a) condensation product of acetaldehyde

b) addition product of acetaldehyde nd ammonia 

C) addition product of acetone and ammonia 

d) condensation product of acetone

Answer- : d

6) The dihalide Cl-CH2- CH2- CH2- Cl is _______

a) vicinal dihalide

b) nonterminal geminal dihalide

C) terminal geminal

d) polymethylene dihalide

Answer- : c

7) In IUPAC system

is named as_________

a) naphthalene aldehyde

b) naphthalene carbaldehyde

C) dibenzene aldehyde

d) naphanal

Answer- : b

8) what is the IUPAC name of compound when carbonyl atom carbon atom is attached to Phenyl group and ethyl group

a) propanone benzene

b) phenyl propan- 1-one

c) 2 phenyl propan- 1-one

d) propiophenone

Answer- : c

9) Give the IUPAC name________

CH3- CH2-CH__ CH-CH2-CH3

                   |        |

                 CHO- CH3

a) 4-methyl-2-ethyl pentanal

b) 4-ethyl-3-methyl pentanal

c) 2-ethy-3-methyl pentanal

d )4-methyl hexanal

Answer- : c

10) The IUPAC name of the compound

CH3CH(OH)CH2CH(CH3)CHO is_____

a) 3-hydroxy-1-methyl pentanal

b) 4-hydroxy-Z-methyl pentanal

c) 3-hydroxy-f-methyl pentanal

d 4-hydroxy-3-methyl pentanal

Answer- : b

11) The IUPAC name of the compound, CCl3, CHO is

a) chloral

b) trichloroacetaldehyde

c) 1,1,1-trichloro ethanal

d) 2,2,2-trichloro ethanal

Answer- : d

12) The lUPAC name of methyl iso-propyl ketone is________

a) 3-methyl butan-2-one

b) 2-methyl butan-1-one

c) 3-methyl butan-1-one

d) 1,1-dimethyl-2-one

Answer- : a

13) In aldehydes and ketones the carbonyl carbon is_________

a) sp3-hybridised

b) sp2′ hybridised

c) unhybridised

d)sp-hybridised

Answer- : b

14) Polar nature of >C=0 group in aldehydes and ketones results ______

a) intemolecular association

b) hydrogen bonding

c) intermolecular H-bonding

d) intramolecular H-bonding

Answer -: a

15) which of the following decrease the reactivity of aldehyde?

a)+I effect

b) -Ieffect

c) positive electromeric effect

d) negative electromeric effect

Answer -: a

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NCERT MCQ CLASS-12 CHAPTER-11 | CHEMISTRY NCERT MCQ | ALCOHOLS, PHENOLS AND ETHERS | EDUGROWN

In This Post we are  providing Chapter-11 Alcohols, Phenols, and Ethers NCERT MCQ for Class 12 Chemistry which will be beneficial for students. These solutions are updated according to 2021-22 syllabus. These MCQS  can be really helpful in the preparation of Board exams and will provide you with a brief knowledge of the chapter.

NCERT MCQ ON ALCOHOLS, PHENOLS AND ETHERS

Question 1.
Which of the following alcohols gives 2-butenc on dehydration by conc. H2SO4?
(a) 2-methyl propene-2-ol
(b) 2-methyl 1 -propanol
(c) Butane-2-ol
(d) Butane 1-ol

Answer: (c) Butane-2-ol

Question 2.
One mole of ethyl acetate on titmen with an excess of LiAlH4 in dry ether and subsequent acidification produces

(a) 1 mole acetic acid + 1 mole ethyl alcohol
(b) 1 mole ethyl alcohol + 1 mole methyl alcohol
(c) 2 moles of ethyl alcohol
(d) 1 mole of 2-butanol

Answer: (c) 2 moles of ethyl alcohol

Question 3.
Which of the following reagents can not, be used to oxidise primary alcohols to aldehydes?

(a) CrO3 in anhydrous medium
(b) KMnO4 in acidic medium
(c) Pyridinium chlorochromate
(d) Heat in the presence of Cu at 573 K

Answer: (b) KMnO4 in acidic medium

Question 4.
1-Phenylethanol can be prepared by the reaction of benzaldehyde with

(a) methyl bromide
(b) ethyl iodide and magnesium
(c) methyl iodide and magnesium (Grignard reagent’s)
(d) methyl bromide and aluminum bromide

Answer: (c) methyl iodide and magnesium (Grignard reagent’s)

Question 5.
Which of the following alcohols will give the most stable carbocation during dehydration?

(a) 2-methyl-1-propanol
(b) 2-methyl-2-propanol
(c) 1-Butanol
(d) 2-Butanol

Answer: (b) 2-methyl-2-propanol

Question 6.
A compound X with the molecular formula C2H8O can be oxidized to another compound Y whose molecular formulae is C3H6O2. The compound X may be

(a) CH3CH2OCH3
(b) CH3CH2CHO
(c) CH3CH2CH2OH
(d) CH3CHOHCH3

Answer: (c) CH3CH2CH2OH

Question 7.
Order of esterification of alcohols are

(a) 3° > 1° > 2°
(b) 2°> 3° > 1°
(c) 1 ° > 2° > 3°
(d) None of these

Answer: (c) 1 ° > 2° > 3°

Question 8.
What happens when tertiary butyl alcohol is passed over heated copper at 300°C?

(a) Secondary butyl alcohol is formed
(b) 2-methylpropene is formed
(c) 1-butene is formed
(d) Butanol is formed

Answer: (b) 2-methylpropene is formed

Question 9.
Which of the following compounds will be most easily attacked by an electrophile?

MCQ Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers with Answers 1

Answer: (c)

Question 10.
MCQ Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers with Answers 2
In the reaction, X is
(a) (CH3)2C = CHCH3
(b) CH3C = CH
(c) (CH3)2CHCH2CH3
MCQ Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers with Answers 3

Answer: (a) (CH3)2C = CHCH3

Question 11.
What would be the reactant and reagent used to obtain 2, 4-dimenthyl pentan-3-ol?

(a) Propanal and propyl magnesium bromide
(b) 3-methylbutanal and 2-methyl magnesium iodide
(c) 2-dimethylpropanone and methyl magnesium iodide
(d) 2-methylpropanal and isopropyl magnesium iodide

Answer: (d) 2-methylpropanal and isopropyl magnesium iodide

Question 12.
The decreasing order of boiling point of the following alcohols is

(a) 3-methylbuan-2-ol > 2-methylbutan-2-ol > pentan-1-ol
(b) Pentan-1-ol > 3-methylbutan-2-ol > 2-methylbutan-2-ol
(c) 2-methylbutan-2-ol > 3-methylbutan-2-ol > pentan-1-ol
(d) 2-methylbutan-2-ol > pental-1-ol > 3-methylbutan-2-ol

Answer: (b) Pentan-1-ol > 3-methylbutan-2-ol > 2-methylbutan-2-ol

Question 13.
Acid catalyzed dehydration of t-butanol is faster than that of n-butanol because

(a) tertiary carbocation is more stable than primary carbocation
(b) primary carbocation is more stable than tertiary carbocation
(c) t-butanol has a higher boiling point
(d) rearrangement takes place during dehydration of t- butanol

Answer: (a) tertiary carbocation is more stable than primary carbocation

Question 14.
An unknown alcohol is treated with “Lucas reagent” to determine whether the alcohol is primary, secondary or tertiary. Which alcohol reacts fastest and by what mechanism?

(a) Tertiary alcohol by SN2
(b) Secondary alcohol by SN1
(c) Tertiary alcohol by SN1
(d) Secondary alcohol by SN2

Answer: (c) Tertiary alcohol by SN1

Question 15.
An alcohol X when treated with hot cone. H2SO4 gave an alkene Y with formula C4H8. This alkene on ozonolysis gives single product with molecular formula C2H4O. The alcohol is

(a) butan-1-ol,
(b) butan-2-ol
(c) 2-methylpropan-1-ol
(d) 2,2-dimethylbutynal-1-oI

Answer: (b) butan-2-ol


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Class 12th Chapter -10 Vector Algebra | NCERT Maths Solution | NCERT Solution | Edugrown

It is important that you have a strong foundation in Maths Solutions. This can help you immensely in exams. Because there is no paper pattern set for the board exams. Every year there are different twists and turns in questions asked in board exams. While preparing for maths it becomes to go through every bit of detail. Thus, NCERT Solutions Class 12 Maths can help you lay a strong foundation. There solutions of each and every question given in the NCERT 12 Textbook in this article. There are crucial chapters like integration, algebra, and calculus which you can solve easily using these Class 12 Maths solutions. Using these NCERT Maths Class 12 Solutions can give you an edge over the other students.

NCERT Solutions for Class 12 Maths Chapter :10 Vector Algebra

Ex 10.1 Class 12 Maths Question 1.
Represent graphically a displacement of 40km, 30° east of north.
Solution:
A line segment of 2 cm is drawn on the right of OY making an angle of 30° with it. OP = 40 km,
scale 1cm = 20 km. Vector \overrightarrow { OP }  represents displacement of 40 km 30° east of north.
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.1 Q1.1

Ex 10.1 Class 12 Maths Question 2.
Classify the following measures as scalars and vectors.
(i) 10 kg
(ii) 2 metres north- west
(iii) 40°
(iv) 40 watt
(v) 10-19 coulomb
(vi) 20 m/sec².
Solution:
(i) Mass-scalar
(ii) Directed distance-vector
(iii) Temperature-scalar
(iv) Rate of electricity-scalar
(v) Electric charge-vector
(vi) Acceleration-vector

Ex 10.1 Class 12 Maths Question 3.
Classify the following as scalar and vector quantities
(i) time period
(ii) distance
(iii) force
(iv) velocity
(v)work.
Solution:
Scalar Quantity: (i) time period (ii) distance (v) work.
Vector Quantity: (iii) force (iv) velocity

Ex 10.1 Class 12 Maths Question 4.
In a square, identify the following vectors
(i) Co-initial
(ii) Equal
(iii) collinear but not equal
Solution:
(i) Co initial vectors are \overrightarrow { a } ,\overrightarrow { d }
(ii) Equal Vectors are \overrightarrow { b } ,\overrightarrow { d }
(iii) Collinear but not equal vectors are \overrightarrow { a } ,\overrightarrow { c }
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.1 Q4.1

Ex 10.1 Class 12 Maths Question 5.
Answer the following as true or false:
(i) \overrightarrow { a } ,\overrightarrow { -a }  are collinear.
(ii) Two collinear vectors are always equal in magnitude.
(iii) Two vectors having same magnitude are collinear.
(iv) Two collinear vectors having the same magnitude are equal.
Solution:
(i) True
(ii) False
(iii) False
(iv) False.

Ex 10.2 Class 12 Maths Question 1.
Compute the magnitude of the following vectors:
\overrightarrow { a } =\hat { i } +\hat { j } +\hat { k } ,\overrightarrow { b } =\hat { 2i } -\hat { 7j } -\hat { 3k }
\overrightarrow { c } =\frac { 1 }{ \sqrt { 3 } } \hat { i } +\frac { 1 }{ \sqrt { 3 } } \hat { j } -\frac { 1 }{ \sqrt { 3 } } \hat { k }
Solution:
\overrightarrow { a } =\hat { i } +\hat { j } +\hat { k }
\left| \overrightarrow { a } \right| =\sqrt { { 1 }^{ 2 }+{ 1 }^{ 2 }+{ 1 }^{ 2 } }
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.2 Q1.1

Ex 10.2 Class 12 Maths Question 2.
Write two different vectors having same magnitude.
Solution:
\overrightarrow { a } =\hat { i } +\hat { 2j } +\hat { 3k } ,\overrightarrow { b } =\hat { 3i } +\hat { 2j } +\hat { k }
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.2 Q2.1
Such possible answers are infinite

Ex 10.2 Class 12 Maths Question 3.
Write two different vectors having same direction.
Solution:
Let the two vectors be
\overrightarrow { a } =\hat { i } +\hat { j } +\hat { k } ,\overrightarrow { b } =\hat { 3i } +\hat { 3j } +\hat { 3k }
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.2 Q3.1
Hence vectors \overrightarrow { a } ,\overrightarrow { b }  have the same direction but different magnitude

Ex 10.2 Class 12 Maths Question 4.
Find the values of x and y so that the vectors \overrightarrow { 2i } +\overrightarrow { 3j } \quad and\quad \hat { xi } +\hat { yj }  are equal.
Solution:
We are given \overrightarrow { 2i } +\overrightarrow { 3j } \quad and\quad \hat { xi } +\hat { yj }
If vectors are equal, then their respective components are equal. Hence x = 2, y = 3.

Ex 10.2 Class 12 Maths Question 5.
Find the scalar and vector components of the vector with initial point (2,1) and terminal point (-5,7).
Solution:
LetA(2, 1) be the initial point and B(-5,7) be the terminal point \overrightarrow { AB } =\left( { x }_{ 2 }-{ x }_{ 1 } \right) \hat { i } +\left( { y }_{ 2 }-{ y }_{ 1 } \right) \hat { j } =-\hat { 7i } +\hat { 6j }
∴The vector components are -\hat { 7i } and\hat { 6j }  and scalar components are – 7 and 6.

Ex 10.2 Class 12 Maths Question 6.
Find the sum of three vectors:
\overrightarrow { a } =\hat { i } -\hat { 2j } +\hat { k } ,\overrightarrow { b } =-2\hat { i } +\hat { 4j } +5\hat { k } \quad and\quad \overrightarrow { c } =\hat { i } -\hat { 6j } -\hat { 7k } ,
Solution:
\overrightarrow { a } =\hat { i } -\hat { 2j } +\hat { k } ,\overrightarrow { b } =-2\hat { i } +\hat { 4j } +5\hat { k } \quad and\quad \overrightarrow { c } =\hat { i } -\hat { 6j } -\hat { 7k } ,
\overrightarrow { a } +\overrightarrow { b } +\overrightarrow { c } =\hat { 0i } -\hat { 4j } -\hat { k } =-4\hat { i } -\hat { k }

Ex 10.2 Class 12 Maths Question 7.
Find the unit vector in the direction of the vector
\overrightarrow { a } =\hat { i } +\hat { j } +\hat { 2k }
Solution:
\overrightarrow { a } =\hat { i } +\hat { j } +\hat { 2k }
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.2 Q18.2

Ex 10.2 Class 12 Maths Question 8.
Find the unit vector in the direction of vector \overrightarrow { PQ } , where P and Q are the points (1,2,3) and (4,5,6) respectively.
Solution:
The points P and Q are (1, 2, 3) and (4, 5, 6) respectively
\overrightarrow { PQ } =(4-1)\hat { i } +(5-2)\hat { j } +(6-3)\hat { k }
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.2 Q8.1

Ex 10.2 Class 12 Maths Question 9.
For given vectors \overrightarrow { a } =2\hat { i } -\hat { j } +2\hat { k } \quad and\quad \overrightarrow { b } =-\hat { i } +\hat { j } -\hat { k }  find the unit vector in the direction of the vector \overrightarrow { a } +\overrightarrow { b }
Solution:
\overrightarrow { a } =2\hat { i } -\hat { j } +2\hat { k } \quad and\quad \overrightarrow { b } =-\hat { i } +\hat { j } -\hat { k }
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.2 Q9.1

Ex 10.2 Class 12 Maths Question 10.
Find a vector in the direction of 5\hat { i } -\hat { j } +2\hat { k }  which has magnitude 8 units.
Solution:
The given vector is \overrightarrow { a } =5\hat { i } -\hat { j } +2\hat { k }
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.2 Q10.1

Ex 10.2 Class 12 Maths Question 11.
Show that the vector 2\hat { i } -3\hat { j } +4\hat { k } \quad and\quad -4\hat { i } +6\hat { j } -8\hat { k }  are collinear.
Solution:
\overrightarrow { a } =2\hat { i } -3\hat { j } +4\hat { k } \quad and\quad \overrightarrow { b } =-4\hat { i } +6\hat { j } -8\hat { k }
=-2(2\hat { i } -3\hat { j } +4\hat { k } )
vector \overrightarrow { a } \quad and\quad \overrightarrow { b }  have the same direction they are collinear.

Ex 10.2 Class 12 Maths Question 12.
Find the direction cosines of the vector \hat { i } +2\hat { j } +3\hat { k }
Solution:
let \overrightarrow { p } =\hat { i } +2\hat { j } +3\hat { k }
Now a = 1,b = 2,c = 3
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.2 Q12.1

Ex 10.2 Class 12 Maths Question 13.
Find the direction cosines of the vector joining the points A (1,2, -3) and B(-1, -2,1), directed fromAtoB.
Solution:
Vector joining the points A and B is
({ x }_{ 2 }-{ x }_{ 1 })\hat { i } +({ y }_{ 2 }-{ y }_{ 1 })\hat { j } +({ z }_{ 2 }-{ z }_{ 1 })\hat { k }
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.2 Q13.1

Ex 10.2 Class 12 Maths Question 14.
Show that the vector \hat { i } +\hat { j } +\hat { k }  are equally inclined to the axes OX, OY, OZ.
Solution:
Let \hat { i } +\hat { j } +\hat { k } =\overrightarrow { a }  , Direction cosines of vector x\hat { i } +y\hat { j } +z\hat { k }  are
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.2 Q14.1
which shows that the vector a is equally inclined to the axes OX, OY, OZ.

Ex 10.2 Class 12 Maths Question 15.
Find the position vector of a point R which divides the line joining the points whose positive vector are P(\hat { i } +2\hat { j } -\hat { k } )\quad and\quad Q(-\hat { i } +\hat { j } +\hat { k } ) in the ratio 2:1
(i) internally
(ii) externally.
Solution:
(i) The point R which divides the line joining the point P(\overrightarrow { a } )\quad and\quad Q(\overrightarrow { b } ) in the ratio m : n
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.2 Q15.1

Ex 10.2 Class 12 Maths Question 16.
Find position vector of the mid point of the vector joining the points P (2,3,4) and Q (4,1, -2).
Solution:
Let \overrightarrow { OP } =2\hat { i } +3\hat { j } +4\hat { k } \quad and\quad \overrightarrow { OQ } =4\hat { i } +\hat { j } -2\hat { k }
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.2 Q16.1

Ex 10.2 Class 12 Maths Question 17.
Show that the points A, B and C with position vector \overrightarrow { a } =3\hat { i } -4\hat { j } -4\hat { k } ,\overrightarrow { b } =2\hat { i } -\hat { j } +\hat { k } and\quad \overrightarrow { c } =\hat { i } -3\hat { j } -5\hat { k }  respectively form the vertices of a right angled triangle.
Solution:
\overrightarrow { AB } =\overrightarrow { b } -\overrightarrow { a } =-\hat { i } +3\hat { j } +5\hat { k }
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.2 Q17.1

Ex 10.2 Class 12 Maths Question 18.
In triangle ABC (fig.), which of the following is not
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.2 Q18.1
(a) \overrightarrow { AB } +\overrightarrow { BC } +\overrightarrow { CA } =\overrightarrow { 0 }
(b) \overrightarrow { AB } +\overrightarrow { BC } -\overrightarrow { AC } =\overrightarrow { 0 }
(c) \overrightarrow { AB } +\overrightarrow { BC } -\overrightarrow { CA } =\overrightarrow { 0 }
(d) \overrightarrow { AB } -\overrightarrow { CB } +\overrightarrow { CA } =\overrightarrow { 0 }
Solution:
We know that
\overrightarrow { AB } +\overrightarrow { BC } +\overrightarrow { CA } =\overrightarrow { 0 }
\overrightarrow { AB } +\overrightarrow { BC } -\overrightarrow { AC } =\overrightarrow { 0 }
Hence option (c) is not correct

Ex 10.2 Class 12 Maths Question 19.
If \overrightarrow { a } ,\overrightarrow { b }  are two collinear vectors then which of the following are incorrect:
(a) \overrightarrow { b } =\lambda \overrightarrow { a } , for some scalar λ.
(b) \overrightarrow { a } =\pm \overrightarrow { b }
(c) the respective components of \overrightarrow { a } ,\overrightarrow { b }  are proportional.
(d) both the vectors \overrightarrow { a } ,\overrightarrow { b }  have same direction, but different magnitudes.
Solution:
Options (d) is incorrect since both the vectors \overrightarrow { a } ,\overrightarrow { b }  , being collinear, are not necessarily in the same direction. They may have opposite directions. Their magnitudes may be different.

Ex 10.3 Class 12 Maths Question 1.
Find the angle between two vectors \overrightarrow { a } ,\overrightarrow { b }  with magnitudes √3 and 2 respectively, and such that \overrightarrow { a } \cdot \overrightarrow { b } =\sqrt { 6 }
Solution:
Angle θ between two vectors \overrightarrow { a } ,\overrightarrow { b } ,
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.3 Q1.1

Ex 10.3 Class 12 Maths Question 2.
Find the angle between the vectors \hat { i } -2\hat { j } +3\hat { k } \quad and\quad 3\hat { i } -2\hat { j } +\hat { k }
Solution:
Let \overrightarrow { a } =\hat { i } -2\hat { j } +3\hat { k } \quad and\quad \overrightarrow { b } =3\hat { i } -2\hat { j } +\hat { k }
Let θ be the angle between \overrightarrow { a } ,\overrightarrow { b } ,
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.3 Q2.1

Ex 10.3 Class 12 Maths Question 3.
Find the projection of the vector \overrightarrow { i } -\overrightarrow { j } , on the line represented by the vector \overrightarrow { i } +\overrightarrow { j } ,
Solution:
let \overrightarrow { a } =\hat { i } -\hat { j } \quad and\quad \overrightarrow { b } =\hat { i } +\hat { j }
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.3 Q3.1

Ex 10.3 Class 12 Maths Question 4.
Find the projection of the vector \hat { i } +3\hat { j } +7\hat { k }  on the vector 7\hat { i } -\hat { j } +8\hat { k }
Solution:
let \overrightarrow { a } =\hat { i } +3\hat { j } +7\hat { k } \quad and\quad \overrightarrow { b } =7\hat { i } -\hat { j } +8\hat { k }  then
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.3 Q4.1

Ex 10.3 Class 12 Maths Question 5.
Show that each of the given three vectors is a unit vector \frac { 1 }{ 7 } \left( 2\hat { i } +3\hat { j } +6\hat { k } \right) ,\frac { 1 }{ 7 } \left( 3\hat { i } -6\hat { j } +2\hat { k } \right) ,\frac { 1 }{ 7 } \left( 6\hat { i } +2\hat { j } -3\hat { k } \right)  Also show that they are mutually perpendicular to each other.
Solution:
Let\quad \overrightarrow { a } =\frac { 1 }{ 7 } \left( 2\hat { i } +3\hat { j } +6\hat { k } \right) ,\overrightarrow { b } =\frac { 1 }{ 7 } \left( 3\hat { i } -6\hat { j } +2\hat { k } \right) ,\overrightarrow { c } =\frac { 1 }{ 7 } \left( 6\hat { i } +2\hat { j } -3\hat { k } \right)
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.3 Q5.1

Ex 10.3 Class 12 Maths Question 6.
Find\left| \overrightarrow { a } \right| and\left| \overrightarrow { b } \right| if\left( \overrightarrow { a } +\overrightarrow { b } \right) \cdot \left( \overrightarrow { a } -\overrightarrow { b } \right) =8\quad and\left| \overrightarrow { a } \right| =8\left| \overrightarrow { b } \right|
Solution:
Given \left( \overrightarrow { a } +\overrightarrow { b } \right) \cdot \left( \overrightarrow { a } -\overrightarrow { b } \right) =8
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.3 Q6.1

Ex 10.3 Class 12 Maths Question 7.
Evaluate the product :
\left( 3\overrightarrow { a } -5\overrightarrow { b } \right) \cdot \left( 2\overrightarrow { a } +7\overrightarrow { b } \right)
Solution:
\left( 3\overrightarrow { a } -5\overrightarrow { b } \right) \cdot \left( 2\overrightarrow { a } +7\overrightarrow { b } \right)
=6\overrightarrow { a } .\overrightarrow { a } -10\overrightarrow { b } \overrightarrow { a } +21\overrightarrow { a } .\overrightarrow { b } -35\overrightarrow { b } .\overrightarrow { b }
=6{ \left| \overrightarrow { a } \right| }^{ 2 }-11\overrightarrow { a } \overrightarrow { b } -35{ \left| \overrightarrow { b } \right| }^{ 2 }

Ex 10.3 Class 12 Maths Question 8.
Find the magnitude of two vectors \overrightarrow { a } ,\overrightarrow { b }  having the same magnitude and such that the angle between them is 60° and their scalar product is \frac { 1 }{ 2 }
Solution:
We know that \overrightarrow { a } .\overrightarrow { b } =\left| \overrightarrow { a } \right| \left| \overrightarrow { b } \right| cos\theta
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.3 Q8.1

Ex 10.3 Class 12 Maths Question 9.
Find \left| \overrightarrow { x } \right|  , if for a unit vector \overrightarrow { a } ,(\overrightarrow { x } -\overrightarrow { a } )\cdot (\overrightarrow { x } +\overrightarrow { a } )=12
Solution:
Given
\overrightarrow { a } ,(\overrightarrow { x } -\overrightarrow { a } )\cdot (\overrightarrow { x } +\overrightarrow { a } )=12
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.3 Q9.1

Ex 10.3 Class 12 Maths Question 10.
If \overrightarrow { a } =2\hat { i } +2\hat { j } +3\hat { k } ,\overrightarrow { b } =-\hat { i } +2\hat { j } +\hat { k } and\overrightarrow { c } =3\hat { i } +\hat { j }  such that \overrightarrow { a } +\lambda \overrightarrow { b } \bot \overrightarrow { c }  , then find the value of λ.
Solution:
Given
\overrightarrow { a } =2\hat { i } +2\hat { j } +3\hat { k } ,\overrightarrow { b } =-\hat { i } +2\hat { j } +\hat { k } and\overrightarrow { c } =3\hat { i } +\hat { j }
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.3 Q10.1

Ex 10.3 Class 12 Maths Question 11.
Show that \left| \overrightarrow { a } \right| \overrightarrow { b } +\left| \overrightarrow { b } \right| a\quad \bot \quad \left| \overrightarrow { a } \right| \cdot \overrightarrow { b } -\left| \overrightarrow { b } \right| a for any two non-zero vectors \overrightarrow { a } ,\overrightarrow { b }
Solution:
\overrightarrow { a } ,\overrightarrow { b }  are any two non zero vectors
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.3 Q11.1

Ex 10.3 Class 12 Maths Question 12.
If \overrightarrow { a } \cdot \overrightarrow { a } =0\quad and\quad \overrightarrow { a } \cdot \overrightarrow { b } =0, then what can be concluded about the vector \overrightarrow { b }  ?
Solution:
\overrightarrow { a } \overrightarrow { a } =0\quad and\quad \overrightarrow { a } .\overrightarrow { b } =0 ,
=> \overrightarrow { b }  = 0
Hence b is any vector.

Ex 10.3 Class 12 Maths Question 13.
If \overrightarrow { a } ,\overrightarrow { b } ,\overrightarrow { c }  are the unit vector such that \overrightarrow { a } +\overrightarrow { b } +\overrightarrow { c } =0 , then find the value of \overrightarrow { a } .\overrightarrow { b } +\overrightarrow { b } .\overrightarrow { c } +\overrightarrow { c } .\overrightarrow { a }
Solution:
We have
\overrightarrow { a } +\overrightarrow { b } +\overrightarrow { c } =0
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.3 Q13.1

Ex 10.3 Class 12 Maths Question 14.
If either vector \overrightarrow { a } =0\quad or\quad \overrightarrow { b } =0 then \overrightarrow { a } .\overrightarrow { b } =0. But the converse need not be true. Justify your answer with an example.
Solution:
Given: \overrightarrow { a } =0\quad or\quad \overrightarrow { b } =0
To prove: \overrightarrow { a } .\overrightarrow { b } =0
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.3 Q14.1

Ex 10.3 Class 12 Maths Question 15.
If the vertices A,B,C of a triangle ABC are (1,2,3) (-1,0,0), (0,1,2) respectively, then find ∠ABC.
Solution:
Let O be the origin then.
\frac { 1 }{ 2 }
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.3 Q15.1

Ex 10.3 Class 12 Maths Question 16.
Show that the points A (1,2,7), B (2,6,3) and C (3,10, -1) are collinear.
Solution:
The position vectors of points A, B, C are
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.3 Q16.1

Ex 10.3 Class 12 Maths Question 17.
Show that the vectors 2\hat { i } -\hat { j } +\hat { k } ,\hat { i } -3\hat { j } -5\hat { k }  and \left( 3\hat { i } -4\hat { j } -4\hat { k } \right)  from the vertices of a right angled triangle.
Solution:
The position vectors of the points A, B and C are
2\hat { i } -\hat { j } +\hat { k } ,\hat { i } -3\hat { j } -5\hat { k }  and \left( 3\hat { i } -4\hat { j } -4\hat { k } \right)
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.3 Q17.1

Ex 10.3 Class 12 Maths Question 18.
If \overrightarrow { a }  is a non-zero vector of magnitude ‘a’ and λ is a non- zero scalar, then λ \overrightarrow { a }  is unit vector if
(a) λ = 1
(b) λ = – 1
(c) a = |λ|
(d) a = \frac { 1 }{ \left| \lambda \right| }
Solution:
\left| \overrightarrow { a } \right| =a
Given : \lambda \overrightarrow { a }  is a unit vectors
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.3 Q18.1

Ex 10.4 Class 12 Maths Question 1.
Find \left| \overrightarrow { a } \times \overrightarrow { b } \right| ,if\quad \overrightarrow { a } =\hat { i } -7\hat { j } +7\hat { k } \quad and\quad \overrightarrow { b } =3\hat { i } -2\hat { j } +2\hat { k }
Solution:
Given
\overrightarrow { a } =\hat { i } -7\hat { j } +7\hat { k } \quad and\quad \overrightarrow { b } =3\hat { i } -2\hat { j } +2\hat { k }
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.4 Q1.1

NCERT Maths Class 12 Chapter 10

Ex 10.4 Class 12 Maths Question 2.
Find a unit vector perpendicular to each of the vector \overrightarrow { a } +\overrightarrow { b } \quad and\quad \overrightarrow { a } -\overrightarrow { b } , where \overrightarrow { a } =3\hat { i } +2\hat { j } +2\hat { k } \quad and\quad \overrightarrow { b } =\hat { i } +2\hat { j } -2\hat { k }
Solution:
we have
\overrightarrow { a } =3\hat { i } +2\hat { j } +2\hat { k } \quad and\quad \overrightarrow { b } =\hat { i } +2\hat { j } -2\hat { k }
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.4 Q2.1

Ex 10.4 Class 12 Maths Question 3.
If a unit vector \overrightarrow { a }  makes angle \frac { \pi }{ 3 } with\quad \hat { i } ,\frac { \pi }{ 4 } with\quad \hat { j }  and an acute angle θ with \overrightarrow { k } ,then find θ and hence the components of \overrightarrow { a } .
Solution:
Let\quad \overrightarrow { a } ={ a }_{ 1 }\hat { i } +{ a }_{ 2 }\hat { j } +{ a }_{ 3 }\hat { k } such\quad that\quad \left| \overrightarrow { a } \right| =1
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.4 Q3.1

Ex 10.4 Class 12 Maths Question 4.
Show that \left( \overrightarrow { a } -\overrightarrow { b } \right) \times \left( \overrightarrow { a } +\overrightarrow { b } \right) =2\left( \overrightarrow { a } \times \overrightarrow { b } \right)
Solution:
LHS = \left( \overrightarrow { a } -\overrightarrow { b } \right) \times \left( \overrightarrow { a } +\overrightarrow { b } \right)
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.4 Q4.1

Ex 10.4 Class 12 Maths Question 5.
Find λ and μ if
\left( 2\hat { i } +6\hat { j } +27\hat { k } \right) \times \left( \hat { i } +\lambda \hat { j } +\mu \hat { k } \right) =0
Solution:
\left( 2\hat { i } +6\hat { j } +27\hat { k } \right) \times \left( \hat { i } +\lambda \hat { j } +\mu \hat { k } \right) =0
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.4 Q5.1

Ex 10.4 Class 12 Maths Question 6.
Given that \overrightarrow { a } .\overrightarrow { b } =0\quad and\quad \overrightarrow { a } \times \overrightarrow { b } =0. What can you conclude about the vectors \overrightarrow { a } ,\overrightarrow { b }  ?
Solution:
\overrightarrow { a } .\overrightarrow { b } =0\quad and\quad \overrightarrow { a } \times \overrightarrow { b } =0
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.4 Q6.1

Ex 10.4 Class 12 Maths Question 7.
Let the vectors \overrightarrow { a } ,\overrightarrow { b } ,\overrightarrow { c }  are given { a }_{ 1 }\hat { i } +{ a }_{ 2 }\hat { j } +{ a }_{ 3 }\hat { k } ,{ b }_{ 1 }\hat { i } +{ b }_{ 2 }\hat { j } +{ b }_{ 3 }\hat { k } ,{ c }_{ 1 }\hat { i } +{ c }_{ 2 }\hat { j } +{ c }_{ 3 }\hat { k } . Then show that \overrightarrow { a } \times \left( \overrightarrow { b } +\overrightarrow { c } \right) =\overrightarrow { a } \times \overrightarrow { b } +\overrightarrow { a } \times \overrightarrow { c }
Solution:
Given
\overrightarrow { a } ,\overrightarrow { b } ,\overrightarrow { c }  are given { a }_{ 1 }\hat { i } +{ a }_{ 2 }\hat { j } +{ a }_{ 3 }\hat { k } ,{ b }_{ 1 }\hat { i } +{ b }_{ 2 }\hat { j } +{ b }_{ 3 }\hat { k } ,{ c }_{ 1 }\hat { i } +{ c }_{ 2 }\hat { j } +{ c }_{ 3 }\hat { k }
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.4 Q7.1

Ex 10.4 Class 12 Maths Question 8.
If either \overrightarrow { a } =0\quad or\quad \overrightarrow { b } =0\quad then\quad \hat { a } \times \hat { b } =0.Is the
converse true? Justify your answer with an example.
Solution:
\overrightarrow { a } =0\Rightarrow \left| \overrightarrow { a } \right| =0
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.4 Q8.1

Ex 10.4 Class 12 Maths Question 9.
Find the area of the triangle with vertices A (1,1,2), B (2,3,5) and C (1,5,5).
Solution:
A (1,1,2), B (2,3,5) and C (1,5,5).
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra 9
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.4 Q9.1

Ex 10.4 Class 12 Maths Question 10.
Find the area of the parallelogram whose adjacent sides are determined by the vectors \overrightarrow { a } =\hat { i } -\hat { j } +3\hat { k } ,\overrightarrow { b } =2\hat { i } -7\hat { j } +\hat { k }
Solution:
We have \overrightarrow { a } =\hat { i } -\hat { j } +3\hat { k } ,\overrightarrow { b } =2\hat { i } -7\hat { j } +\hat { k }
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.4 Q10.1

Ex 10.4 Class 12 Maths Question 11.
Let the vectors\overrightarrow { a } ,\overrightarrow { b }  such that \left| \overrightarrow { a } \right| =3,\left| \overrightarrow { b } \right| =\frac { \sqrt { 2 } }{ 3 }  then \overrightarrow { a } \times \overrightarrow { b }  is a unit vector if the angle between \overrightarrow { a } ,\overrightarrow { b }  is
(a) \frac { \pi }{ 6 }
(b) \frac { \pi }{ 4 }
(c) \frac { \pi }{ 3 }
(d) \frac { \pi }{ 2 }
Solution:
Given
\left| \overrightarrow { a } \times \overrightarrow { b } \right| =1
\left| \overrightarrow { a } \right| =3,\left| \overrightarrow { b } \right| =\frac { \sqrt { 2 } }{ 3 }
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.4 Q11.1

Ex 10.4 Class 12 Maths Question 12.
Area of a rectangles having vertices
A\left( -\hat { i } +\frac { 1 }{ 2 } \hat { j } +4\hat { k } \right) ,B\left( \hat { i } +\frac { 1 }{ 2 } \hat { j } +4\hat { k } \right) ,
C\left( \hat { i } -\frac { 1 }{ 2 } \hat { j } +4\hat { k } \right) ,D\left( -\hat { i } -\frac { 1 }{ 2 } \hat { j } +4\hat { k } \right) ,
(a) \frac { 1 }{ 2 } sq units
(b) 1sq.units
(c) 2sq.units
(d) 4sq.units
Solution:
\overrightarrow { OA } =\left( -\hat { i } +\frac { 1 }{ 2 } \hat { j } +4\hat { k } \right)
\overrightarrow { OB } =\left( \hat { i } +\frac { 1 }{ 2 } \hat { j } +4\hat { k } \right)
NCERT Solutions for Class 12 Maths Chapter 10 Vector Algebra Ex 10.4 Q12.1

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Class 12th Chapter -9 Differential Equations | NCERT Maths Solution | NCERT Solution | Edugrown

It is important that you have a strong foundation in Maths Solutions. This can help you immensely in exams. Because there is no paper pattern set for the board exams. Every year there are different twists and turns in questions asked in board exams. While preparing for maths it becomes to go through every bit of detail. Thus, NCERT Solutions Class 12 Maths can help you lay a strong foundation. There solutions of each and every question given in the NCERT 12 Textbook in this article. There are crucial chapters like integration, algebra, and calculus which you can solve easily using these Class 12 Maths solutions. Using these NCERT Maths Class 12 Solutions can give you an edge over the other students.

NCERT Solutions for Class 12 Maths Chapter :9 Differential Equations

Determine order and degree (if defined) of the differential equations given in Questions 1 to 10.

Looking for a tool that does Partial Derivation easily? Utilize our Partial Derivative Calculator tool and obtain the result instantly.

Ex 9.1 Class 12 Maths Question 1.
\frac { { d }^{ 4 }y }{ { dx }^{ 4 } } +({ sin }y^{ III })=0
Solution:
Order of the equation is 4
It is not a polynomial in derivatives so that it
has not degree.

Ex 9.1 Class 12 Maths Question 2.
{ y }^{ I }+5y=0
Solution:
{ y }^{ I }+5y=0
It is a D.E. of order one and degree one.

Ex 9.1 Class 12 Maths Question 3.
{ \left( \frac { ds }{ dt } \right) }^{ 4 }+3s{ \left( \frac { { d }^{ 2 }s }{ { dt }^{ 2 } } \right) }=0
Solution:
Order of the equation is 2.
Degree of the equation is

Ex 9.1 Class 12 Maths Question 4.
{ \left( \frac { { d }^{ 2 }y }{ { dx }^{ 2 } } \right) }^{ 2 }+cos\left( \frac { dy }{ dx } \right) =0
Solution:
{ \left( \frac { { d }^{ 2 }y }{ { dx }^{ 2 } } \right) }^{ 2 }+cos\left( \frac { dy }{ dx } \right) =0
It is a D.E. of order 2 and degree undefined

Ex 9.1 Class 12 Maths Question 5.
\frac { { d }^{ 2 }y }{ { dx }^{ 2 } } =cos3x+sin3x
Solution:
\frac { { d }^{ 2 }y }{ { dx }^{ 2 } } =cos3x+sin3x
It is a D.E. of order 2 and degree 1.

Ex 9.1 Class 12 Maths Question 6.
{ { (y }^{ III }) }^{ 2 }+{ { ( }y^{ II }) }^{ 3 }+{ { (y }^{ I }) }^{ 4 }+{ y }^{ 5 }=0
Solution:
Order of the equation is 3
Degree of the equation is 2

Ex 9.1 Class 12 Maths Question 7.
{ { y }^{ III } }+{ 2y^{ II } }+{ { y }^{ I } }=0
Solution:
{ { y }^{ III } }+{ 2y^{ II } }+{ { y }^{ I } }=0
The highest order derivative is y.
Thus the order of the D.E. is 3.
The degree of D.E is 1

Ex 9.1 Class 12 Maths Question 8.
{ y }^{ I }+y={ e }^{ x }
Solution:
{ y }^{ I }+y={ e }^{ x }
The order of the D. E. = 1 (highest order derivative)
The degree of the D.E. = 1.

Ex 9.1 Class 12 Maths Question 9.
{ y }^{ III }+{ { (y }^{ I }) }^{ 2 }+2y=0
Solution:
{ y }^{ III }+{ { (y }^{ I }) }^{ 2 }+2y=0
The highest derivative is 2.
Order of the D.E. = 2.
Degree of the D. E = 1

Ex 9.1 Class 12 Maths Question 10.
{ y }^{ II }+{ { 2y }^{ I } }+siny=0
Solution:
Order of the equation is 2
Degree of the equation is 1

Ex 9.1 Class 12 Maths Question 11.
The degree of the differential equation
{ \left( \frac { { d }^{ 2 }y }{ { dx }^{ 2 } } \right) }^{ 3 }{ +\left( \frac { dy }{ dx } \right) }^{ 2 }+sin{ \left( \frac { dy }{ dx } \right) }+1=0
(a) 3
(b) 2
(c) 1
(d) not defined
Solution:
{ \left( \frac { { d }^{ 2 }y }{ { dx }^{ 2 } } \right) }^{ 3 }{ +\left( \frac { dy }{ dx } \right) }^{ 2 }+sin{ \left( \frac { dy }{ dx } \right) }+1=0
The degree not defined.
Because the differential equation can not be written as a polynomial in all the differential coefficients.
Hence option (d) is correct.

Ex 9.1 Class 12 Maths Question 12.
The order of the differential equation
{ 2x }^{ 2 }\frac { { d }^{ 2 }y }{ { dx }^{ 2 } } -3\frac { dy }{ dx } +y=0
(a) 2
(b) 1
(c) 0
(d) not defined
Solution:
{ 2x }^{ 2 }\frac { { d }^{ 2 }y }{ { dx }^{ 2 } } -3\frac { dy }{ dx } +y=0
Thus order of the D.E. = 2
Hence option (a) is correct.

Verify that the given functions (explicit or implicit) is a solution of the corresponding differential equation

Ex 9.2 Class 12 Maths Question 1.
y={ e }^{ x }+1:{ y }^{ II }-{ y }^{ I }=0
Solution:
y={ e }^{ x }+1:{ y }^{ II }-{ y }^{ I }=0
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.2 Q1.1

Ex 9.2 Class 12 Maths Question 2.
y=x^{ 2 }+2x+c:{ y }^{ I }-2x-2=0
Solution:
y=x^{ 2 }+2x+c:{ y }^{ I }-2x-2=0
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.2 Q2.1

Ex 9.2 Class 12 Maths Question 3.
y=cosx+c:{ y }^{ I }+sinx=0
Solution:
y=cosx+c:{ y }^{ I }+sinx=0
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.2 Q3.1

Ex 9.2 Class 12 Maths Question 4.
y=\sqrt { 1+{ x }^{ 2 } } :{ y }^{ I }=\frac { xy }{ 1+{ x }^{ 2 } }
Solution:
y=\sqrt { 1+{ x }^{ 2 } } :{ y }^{ I }=\frac { xy }{ 1+{ x }^{ 2 } }
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.2 Q4.1

Ex 9.2 Class 12 Maths Question 5.
y=Ax:x{ y }^{ I }=y(x\neq 0)
Solution:
y=Ax:x{ y }^{ I }=y(x\neq 0)
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.2 Q5.1

Ex 9.2 Class 12 Maths Question 6.
y=x\quad sinx;{ xy }^{ I }=y+x\sqrt { { x }^{ 2 }-{ y }^{ 2 } } (x\neq 0\quad and\quad x>y\quad or\quad x<-y)
Solution:
y=x\quad sinx;{ xy }^{ I }=y+x\sqrt { { x }^{ 2 }-{ y }^{ 2 } } (x\neq 0\quad and\quad x>y\quad or\quad x<-y)
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.2 Q6.1

Ex 9.2 Class 12 Maths Question 7.
xy = logy + C,
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.2 Q7.1
Solution:
xy = logy + C,
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.2 Q7.2

Ex 9.2 Class 12 Maths Question 8.
y-cosy=x:(ysiny+cosy+x){ y }^{ I }=y
Solution:
y-cosy=x:(ysiny+cosy+x){ y }^{ I }=y
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.2 Q8.1

Ex 9.2 Class 12 Maths Question 9.
x+y={ ta }n^{ -1 }y;{ y }^{ 2 }{ y }^{ I }+{ y }^{ 2 }+1=0
Solution:
x+y={ ta }n^{ -1 }y;{ y }^{ 2 }{ y }^{ I }+{ y }^{ 2 }+1=0
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.2 Q9.1

Ex 9.2 Class 12 Maths Question 10.
y=\sqrt { { a }^{ 2 }-{ x }^{ 2 } } x\in (-a,a);x+y\frac { dy }{ dx } =0,(y\neq 0)
Solution:
y=\sqrt { { a }^{ 2 }-{ x }^{ 2 } } x\in (-a,a);x+y\frac { dy }{ dx } =0,(y\neq 0)
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.2 Q10.1

Ex 9.2 Class 12 Maths Question 11.
The number of arbitrary constants in the general solution of a differential equation of fourth order are:
(a) 0
(b) 2
(c) 3
(d) 4
Solution:
(b) The general solution of a differential equation of fourth order has 4 arbitrary constants.
Because it contains the same number of arbitrary constants as the order of differential equation.

Ex 9.2 Class 12 Maths Question 12.
The number of arbitrary constants in the particular solution of a differential equation of third order are:
(a) 3
(b) 2
(c) 1
(d) 0
Solution:
(d) Number of arbitrary constants = 0
Because particular solution is free from arbitrary constants.

In each of the following, Q. 1 to 5 form a differential equation representing the given family of curves by eliminating arbitrary constants a and b.

Ex 9.3 Class 12 Maths Question 1.
\frac { x }{ a } +\frac { y }{ b } =1
Solution:
Given that \frac { x }{ a } +\frac { y }{ b } =1 …(i)
differentiating (i) w.r.t x, we get
\frac { 1 }{ a } +\frac { 1 }{ b } { y }^{ I }=0 …(ii)
again differentiating w.r.t x, we get
\frac { 1 }{ b } { y }^{ II }=0\Rightarrow { y }^{ II }=0
which is the required differential equation

Ex 9.3 Class 12 Maths Question 2.
y² = a(b² – x²)
Solution:
given that
y² = a(b² – x²)…(i)
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.3 Q2.1

Ex 9.3 Class 12 Maths Question 3.
y = ae3x+be-2x
Solution:
Given that
y = ae3x+be-2x …(i)
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.3 Q3.1

Ex 9.3 Class 12 Maths Question 4.
y = e2x (a+bx)
Solution:
y = e2x (a+bx)
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.3 Q4.1

Ex 9.3 Class 12 Maths Question 5.
y = ex(a cosx+b sinx)
Solution:
The curve y = ex(a cosx+b sinx) …(i)
differentiating w.r.t x
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.3 Q5.1

Ex 9.3 Class 12 Maths Question 6.
Form the differential equation of the family of circles touching the y axis at origin
Solution:
The equation of the circle with centre (a, 0) and radius a, which touches y- axis at origin
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.3 Q6.1

Ex 9.3 Class 12 Maths Question 7.
Form the differential equation of the family of parabolas having vertex at origin and axis along positive y-axis.
Solution:
The equation of parabola having vertex at the origin and axis along positive y-axis is
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.3 Q7.1

Ex 9.3 Class 12 Maths Question 8.
Form the differential equation of family of ellipses having foci on y-axis and centre at origin.
Solution:
The equation of family ellipses having foci at y- axis is
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.3 Q8.1

Ex 9.3 Class 12 Maths Question 9.
Form the differential equation of the family of hyperbolas having foci on x-axis and centre at the origin.
Solution:
Equation of the hyperbola is \frac { { x }^{ 2 } }{ { a }^{ 2 } } -\frac { { y }^{ 2 } }{ { b }^{ 2 } } =1
Differentiating both sides w.r.t x
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.3 Q9.1
which is the req. differential eq. of the hyperbola.

Ex 9.3 Class 12 Maths Question 10.
Form the differential equation of the family of circles having centre on y-axis and radius 3 units
Solution:
Let centre be (0, a) and r = 3
Equation of circle is
x² + (y – a)² = 9 …(i)
Differentiating both sides, we get
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.3 Q10.1
which is required equation

Ex 9.3 Class 12 Maths Question 11.
Which of the following differential equation has y={ c }_{ 1 }{ e }^{ x }+{ c }_{ 2 }{ e }^{ -x } as the general solution ?
(a) \frac { { d }^{ 2 }y }{ { dx }^{ 2 } } +y=0
(b) \frac { { d }^{ 2 }y }{ { dx }^{ 2 } } -y=0
(c) \frac { { d }^{ 2 }y }{ { dx }^{ 2 } } +1=0
(d) \frac { { d }^{ 2 }y }{ { dx }^{ 2 } } -1=0
Solution:
(b) y={ c }_{ 1 }{ e }^{ x }+{ c }_{ 2 }{ e }^{ -x }\Rightarrow \frac { dy }{ dx } ={ c }_{ 1 }{ e }^{ x }-{ c }_{ 2 }{ e }^{ -x }
\frac { { d }^{ 2 }y }{ { dx }^{ 2 } } ={ c }_{ 1 }{ e }^{ x }+{ c }_{ 2 }{ e }^{ -x }\Rightarrow \frac { { d }^{ 2 }y }{ { dx }^{ 2 } } -y=0

Ex 9.3 Class 12 Maths Question 12.
Which of the following differential equations has y = x as one of its particular solution ?
(a) \frac { { d }^{ 2 }y }{ { dx }^{ 2 } } -{ x }^{ 2 }\frac { dy }{ dx } +xy=x
(b) \frac { { d }^{ 2 }y }{ { dx }^{ 2 } } +{ x }\frac { dy }{ dx } +xy=x
(c) \frac { { d }^{ 2 }y }{ { dx }^{ 2 } } -{ x }^{ 2 }\frac { dy }{ dx } +xy=0
(d) \frac { { d }^{ 2 }y }{ { dx }^{ 2 } } +{ x }\frac { dy }{ dx } +xy=0
Solution:
(c) y = x
\frac { dy }{ dx } =1,\frac { { d }^{ 2 }y }{ { dx }^{ 2 } } =0
\frac { { d }^{ 2 }y }{ { dx }^{ 2 } } -{ x }^{ 2 }\frac { dy }{ dx } +xy=0

For each of the following D.E in Q. 1 to 10 find the general solution:

Ex 9.4 Class 12 Maths Question 1.
\frac { dy }{ dx } =\frac { 1-cosx }{ 1+cosx }
Solution:
\frac { dy }{ dx } =\frac { 1-cosx }{ 1+cosx }
\frac { dy }{ dx } =\frac { 1-cosx }{ 1+cosx } =\frac { { 2sin }^{ 2 }\left( \frac { x }{ 2 } \right) }{ { 2cos }^{ 2 }\left( \frac { x }{ 2 } \right) } ={ tan }^{ 2 }\left( \frac { x }{ 2 } \right)
integrating both sides, we get
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.4 Q1.1

Ex 9.4 Class 12 Maths Question 2.
\frac { dy }{ dx } =\sqrt { 4-{ y }^{ 2 } } (-2<y<2)
Solution:
\frac { dy }{ dx } =\sqrt { 4-{ y }^{ 2 } } \Rightarrow \int { \frac { dy }{ \sqrt { { 4-y }^{ 2 } } } } =\int { dx }
\Rightarrow { sin }^{ -1 }\frac { y }{ 2 } =x+C
\Rightarrow y=2sin(x+C)

Ex 9.4 Class 12 Maths Question 3.
\frac { dy }{ dx } +y=1(y\neq 1)
Solution:
\frac { dy }{ dx } +y=1\Rightarrow \int { \frac { dy }{ y-1 } } =-\int { dx }
\Rightarrow log(y-1)=-x+c\Rightarrow y=1+{ e }^{ -x }.{ e }^{ c }
Hence\quad y=1+{ Ae }^{ -x }
which is required solution

Ex 9.4 Class 12 Maths Question 4.
sec² x tany dx+sec² y tanx dy = 0
Solution:
we have
sec² x tany dx+sec² y tanx dy = 0
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.4 Q4.1

Ex 9.4 Class 12 Maths Question 5.
\left( { e }^{ x }+{ e }^{ -x } \right) dy-\left( { e }^{ x }-{ e }^{ -x } \right) dx=0
Solution:
we have
\left( { e }^{ x }+{ e }^{ -x } \right) dy-\left( { e }^{ x }-{ e }^{ -x } \right) dx=0
Integrating on both sides
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.4 Q5.1

Ex 9.4 Class 12 Maths Question 6.
\frac { dy }{ dx } =\left( { 1+x }^{ 2 } \right) \left( { 1+y }^{ 2 } \right)
Solution:
\frac { dy }{ { 1+y }^{ 2 } } =\left( { 1+x }^{ 2 } \right) dx
integrating on both side we get
{ tan }^{ -1 }y={ x+\frac { 1 }{ 3 } }x^{ 3 }+c
which is required solution

Ex 9.4 Class 12 Maths Question 7.
y logy dx – x dy = 0
Solution:
\because \quad y\quad logy\quad dx=x\quad dy\Rightarrow \frac { dy }{ y\quad logy } =\frac { dx }{ x }
integrating we get
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.4 Q7.1

Ex 9.4 Class 12 Maths Question 8.
{ x }^{ 5 }\frac { dy }{ dx } =-{ y }^{ 5 }
Solution:
{ x }^{ 5 }\frac { dy }{ dx } =-{ y }^{ 5 }\Rightarrow \int { { y }^{ -5 }dy } =-\int { { x }^{ -5 }dx }
\Rightarrow -\frac { 1 }{ { y }^{ 4 } } =\frac { 1 }{ { x }^{ 4 } } +4c\Rightarrow { x }^{ -4 }+{ y }^{ -4 }=k

Ex 9.4 Class 12 Maths Question 9.
solve the following
\frac { dy }{ dx } ={ sin }^{ -1 }x
Solution:
\frac { dy }{ dx } ={ sin }^{ -1 }x\Rightarrow \int { dy } =\int { { sin }^{ -1 }xdx }
integrating both sides we get
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.4 Q9.1

Ex 9.4 Class 12 Maths Question 10.
{ e }^{ x }tany\quad dx+{ (1-e }^{ x }){ sec }^{ 2 }dy=0
Solution:
{ e }^{ x }tany\quad dx+{ (1-e }^{ x }){ sec }^{ 2 }dy=0
we can write in another form
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.4 Q10.1

Find a particular solution satisfying the given condition for the following differential equation in Q.11 to 14.

Ex 9.4 Class 12 Maths Question 11.
\left( { x }^{ 3 }+{ x }^{ 2 }+x+1 \right) \frac { dy }{ dx } ={ 2x }^{ 2 }+x;y=1,when\quad x=0
Solution:
here
dy=\frac { { 2x }^{ 2 }+x }{ \left( { x }^{ 3 }+{ x }^{ 2 }+x+1 \right) } dx
integrating we get
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.4 Q11.1

Ex 9.4 Class 12 Maths Question 12.
x\left( { x }^{ 2 }-1 \right) \frac { dy }{ dx } =1,y=0\quad when\quad x=2
Solution:
x\left( { x }^{ 2 }-1 \right) \frac { dy }{ dx } =1,y=0\quad when\quad x=2
\Rightarrow \int { dy } =\int { \frac { dy }{ x(x+1)(x-1) } }
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.4 Q12.1

Ex 9.4 Class 12 Maths Question 13.
cos\left( \frac { dy }{ dx } \right) =a,(a\epsilon R),y=1\quad when\quad x=0
Solution:
cos\left( \frac { dy }{ dx } \right) =a\quad \therefore \frac { dy }{ dx } ={ cos }^{ -1 }a
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.4 Q13.1

Ex 9.4 Class 12 Maths Question 14.
\frac { dy }{ dx } =ytanx,y=1\quad when\quad x=0
Solution:
\frac { dy }{ dx } =ytanx\Rightarrow \int { \frac { dy }{ y } } =\int { tanx\quad dx }
=> logy = logsecx + C
When x = 0, y = 1
=> log1 = log sec0 + C => 0 = log1 + C
=> C = 0
∴ logy = log sec x
=> y = sec x.

Ex 9.4 Class 12 Maths Question 15.
Find the equation of the curve passing through the point (0,0) and whose differential equation { y }^{ I }={ e }^{ x }sinx
Solution:
{ y }^{ I }={ e }^{ x }sinx
\Rightarrow dy={ e }^{ x }sinx\quad dx
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.4 Q15.1

Ex 9.4 Class 12 Maths Question 16.
For the differential equation xy\frac { dy }{ dx } =(x+2)(y+2) find the solution curve passing through the point (1,-1)
Solution:
The differential equation isxy\frac { dy }{ dx } =(x+2)(y+2)
or xydy=(x + 2)(y+2)dx
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.4 Q16.1

Ex 9.4 Class 12 Maths Question 17.
Find the equation of a curve passing through the point (0, -2) given that at any point (pc, y) on the curve the product of the slope of its tangent and y-coordinate of the point is equal to the x-coordinate of the point
Solution:
According to the question y\frac { dy }{ dx } =x
\Rightarrow \int { ydy } =\int { xdx } \Rightarrow \frac { { y }^{ 2 } }{ 2 } =\frac { { x }^{ 2 } }{ 2 } +c
0, – 2) lies on it.c = 2
∴ Equation of the curve is : x² – y² + 4 = 0.

Ex 9.4 Class 12 Maths Question 18.
At any point (x, y) of a curve the slope of the tangent is twice the slope of the line segment joining the point of contact to the point (-4,-3) find the equation of the curve given that it passes through (- 2,1).
Solution:
Slope of the tangent to the curve = \frac { dy }{ dx }
slope of the line joining (x, y) and (- 4, – 3)
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.4 Q18.1

Ex 9.4 Class 12 Maths Question 19.
The volume of a spherical balloon being inflated changes at a constant rate. If initially its radius is 3 units and offer 3 seconds it is 6 units. Find the radius of balloon after t seconds.
Solution:
Let v be volume of the balloon.
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.4 Q19.1

Ex 9.4 Class 12 Maths Question 20.
In a bank principal increases at the rate of r% per year. Find the value of r if Rs 100 double itself in 10 years
Solution:
Let P be the principal at any time t.
According to the problem
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.4 Q20.1

Ex 9.4 Class 12 Maths Question 21.
In a bank principal increases at the rate of 5% per year. An amount of Rs 1000 is deposited with this bank, how much will it worth after 10 years
Solution:
Let p be the principal Rate of interest is 5%
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.4 Q21.1

Ex 9.4 Class 12 Maths Question 22.
In a culture the bacteria count is 1,00,000. The number is increased by 10% in 2 hours. In how many hours will the count reach 2,00,000 if the rate of growth of bacteria is proportional to the number present
Solution:
Let y denote the number of bacteria at any instant t • then according to the question
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.4 Q22.1

Ex 9.4 Class 12 Maths Question 23.
The general solution of a differential equation \frac { dy }{ dx } ={ e }^{ x+y }  is
(a) { e }^{ x }+{ e }^{ -y }=c
(b) { e }^{ x }+{ e }^{ y }=c
(c) { e }^{ -x }+{ e }^{ y }=c
(d) { e }^{ -x }+{ e }^{ -y }=c
Solution:
(a) \frac { dy }{ dx } ={ e }^{ x }.{ e }^{ y }\Rightarrow \int { { e }^{ -y }dy } =\int { { e }^{ x }dx }
\Rightarrow { e }^{ -y }={ e }^{ x }+k\Rightarrow { e }^{ x }+{ e }^{ -y }=c

Show that the given differential equation is homogeneous and solve each of them in Questions 1 to 10

Ex 9.5 Class 12 Maths Question 1.
(x²+xy)dy = (x²+y²)dx
Solution:
(x²+xy)dy = (x²+y²)dx
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.5 Q1.1
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.5 Q1.2

Ex 9.5 Class 12 Maths Question 2.
{ y }^{ I }=\frac { x+y }{ x }
Solution:
{ y }^{ I }=\frac { x+y }{ x }
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.5 Q2.1

Ex 9.5 Class 12 Maths Question 3.
(x-y)dy-(x+y)dx=0
Solution:
\frac { dy }{ dx } =\frac { x+y }{ x-y } =\frac { 1+\frac { y }{ x } }{ 1-\frac { y }{ x } }
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.5 Q3.1

Ex 9.5 Class 12 Maths Question 4.
(x²-y²)dx+2xy dy=0
Solution:
\frac { dy }{ dx } =\frac { { y }^{ 2 }-{ x }^{ 2 } }{ 2xy }
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.5 Q4.1

Ex 9.5 Class 12 Maths Question 5.
{ x }^{ 2 }\frac { dy }{ dx } ={ x }^{ 2 }-{ 2y }^{ 2 }+xy
Solution:
\frac { dy }{ dx } =1-2{ \left( \frac { y }{ x } \right) }^{ 2 }+\frac { y }{ x }
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.5 Q5.1

Ex 9.5 Class 12 Maths Question 6.
xdy-ydx=\sqrt { { x }^{ 2 }+{ y }^{ 2 } } dx
Solution:
xdy-ydx=\sqrt { { x }^{ 2 }+{ y }^{ 2 } } dx
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.5 Q6.1

Ex 9.5 Class 12 Maths Question 7.
\left\{ xcos\left( \frac { y }{ x } \right) +ysin\left( \frac { y }{ x } \right) \right\} ydx=\left\{ ysin\left( \frac { y }{ x } \right) -xcos\left( \frac { y }{ x } \right) \right\} xdy
Solution:
\left\{ xcos\left( \frac { y }{ x } \right) +ysin\left( \frac { y }{ x } \right) \right\} ydx=\left\{ ysin\left( \frac { y }{ x } \right) -xcos\left( \frac { y }{ x } \right) \right\} xdy
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.5 Q7.1
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.5 Q7.2
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.5 Q7.3

Ex 9.5 Class 12 Maths Question 8.
x\frac { dy }{ dx } -y+xsin\left( \frac { y }{ x } \right) =0
Solution:
x\frac { dy }{ dx } -y+xsin\left( \frac { y }{ x } \right) =0\Rightarrow \frac { dy }{ dx } =\frac { y }{ x } -sin\frac { y }{ x }
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.5 Q8.1

Ex 9.5 Class 12 Maths Question 9.
ydx+xlog\left( \frac { y }{ x } \right) dy-2xdy=0
Solution:
\frac { dy }{ dx } =\frac { y }{ 2x-xlog\frac { y }{ x } } =\frac { \frac { y }{ x } }{ 2-log\frac { y }{ x } }
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.5 Q9.1

Ex 9.5 Class 12 Maths Question 10.
\left( { 1+e }^{ \frac { x }{ y } } \right) dx+{ e }^{ \frac { x }{ y } }\left( 1-\frac { x }{ y } \right) dy=0
Solution:
\frac { dx }{ dy } =-\frac { { e }^{ \frac { x }{ y } }\left( 1-\frac { x }{ y } \right) }{ { 1+e }^{ \frac { x }{ y } } } =\frac { \left( \frac { x }{ y } -1 \right) { e }^{ \frac { x }{ y } } }{ { 1+e }^{ \frac { x }{ y } } } =f(x,y)
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.5 Q10.1
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.5 Q10.2

For each of the following differential equation in Q 11 to 15 find the particular solution satisfying the given condition:

Ex 9.5 Class 12 Maths Question 11.
(x + y) dy+(x – y)dx = 0,y = 1 when x = 1
Solution:
given
(x + y) dy+(x – y)dx = 0
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.5 Q11.1

Ex 9.5 Class 12 Maths Question 12.
x²dy+(xy+y²)dx=0, y=1 when x=1
Solution:
\frac { dy }{ dx } =\frac { xy+{ y }^{ 2 } }{ { x }^{ 2 } } =f(x,y)
f(x,y) is homogeneous
∴ put y = vx
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.5 Q12.1
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.5 Q12.2

Ex 9.5 Class 12 Maths Question 13.
\left( x{ sin }^{ 2 }\frac { y }{ x } -y \right) dx+xdy=0,y=\frac { \pi }{ 4 } ,when\quad x=1
Solution:
\left( x{ sin }^{ 2 }\frac { y }{ x } -y \right) dx+xdy=0
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.5 Q13.1

Ex 9.5 Class 12 Maths Question 14.
\frac { dy }{ dx } -\frac { y }{ x } +cosec\left( \frac { y }{ x } \right) =0,y=0\quad when\quad x=1
Solution:
\frac { dy }{ dx } -\frac { y }{ x } +cosec\left( \frac { y }{ x } \right) =0
which is a homogeneous differential equation
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.5 Q14.1

Ex 9.5 Class 12 Maths Question 15.
2xy-{ y }^{ 2 }-{ 2x }^{ 2 }\frac { dy }{ dx } =0,y=2,when\quad x=1
Solution:
\frac { dy }{ dx } =\frac { y }{ x } +\frac { 1 }{ 2 } { \left( \frac { y }{ x } \right) }^{ 2 } …(i)
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.5 Q15.1

Ex 9.5 Class 12 Maths Question 16.
A homogeneous equation of the form \frac { dx }{ dy } =h\left( \frac { x }{ y } \right)  can be solved by making the substitution,
(a) y=vx
(b) v=yx
(c) x=vy
(d) x=v
Solution:
(c) option x = vy

Ex 9.5 Class 12 Maths Question 17.
Which of the following is a homogeneous differential equation?
(a) (a) (4x + 6y + 5)dy-(3y + 2x + 4)dx = 0
(b) (xy)dx-({ x }^{ 3 }+{ y }^{ 3 })dy
(c) ({ x }^{ 3 }+{ 2y }^{ 2 })dx+2xydy=0
(d) { y }^{ 2 }dx+{ (x }^{ 2 }-xy-{ y }^{ 2 })dy=0
Solution:
(d)

Find the general solution of the following differential equations in Q.1 to 12

Ex 9.6 Class 12 Maths Question 1.
\frac { dy }{ dx } +2y=sinx
Solution:
Given equation is a linear differential equation of the form \frac { dy }{ dx } +Py=Q;
Here, P = 2, Q = sin x
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.6 Q1.1

Ex 9.6 Class 12 Maths Question 2.
\frac { dy }{ dx } +3y={ e }^{ -2x }
Solution:
\frac { dy }{ dx } +3y={ e }^{ -2x }
Here P = 3, IF={ e }^{ \int { p.dx } }={ e }^{ 3x }
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.6 Q2.1
which is required equation

Ex 9.6 Class 12 Maths Question 3.
\frac { dy }{ dx } +\frac { y }{ x } ={ x }^{ 2 }
Solution:
\frac { dy }{ dx } +\frac { y }{ x } ={ x }^{ 2 }
IF={ e }^{ \int { \frac { 1 }{ x } dx } }={ e }^{ logx }=x
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.6 Q3.1

Ex 9.6 Class 12 Maths Question 4.
\frac { dy }{ dx } +(secx)y=tanx\left( 0\le x<\frac { \pi }{ 2 } \right)
Solution:
Here, P = secx, Q = tanx; IF={ e }^{ \int { p.dx } }={ e }^{ \int { secx.dx } }
={ e }^{ log|secx+tanx| }
= sec x + tan x
i.e., The solu. is y.× I.F. = ∫Q × I.F. dx + c
or y × (secx+tanx) = ∫tanx(secx+tanx)dx+c
Reqd. sol. is
∴ y(secx + tanx) = (secx + tanx)-x + c

Ex 9.6 Class 12 Maths Question 5.
{ cos }^{ 2 }x\frac { dy }{ dx } +y=tanx\left( 0\le x\le \frac { \pi }{ 2 } \right)
Solution:
\frac { dy }{ dx } +{ y\quad sec }^{ 2 }x={ sec }^{ 2 }x\quad tanx
⇒ integrating factor = { e }^{ \int { { sec }^{ 2 }xdx } }={ e }^{ tanx }
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.6 Q5.1

Ex 9.6 Class 12 Maths Question 6.
x\frac { dy }{ dx } +2y={ x }^{ 2 }logx
Solution:
\frac { dy }{ dx } +\frac { 2 }{ x } y\quad =\quad x\quad logx
Here P = \frac { 2 }{ x } and Q = x logx
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.6 Q6.1

Ex 9.6 Class 12 Maths Question 7.
xlogx\frac { dy }{ dx } +y=\frac { 2 }{ x } logx
Solution:
\frac { dy }{ dx } +\frac { 1 }{ xlogx } y=\frac { 2 }{ { x }^{ 2 } }
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.6 Q7.1

Ex 9.6 Class 12 Maths Question 8.
(1+x²)dy+2xy dx = cotx dx(x≠0)
Solution:
(1+x²)dy+2xy dx = cotx dx
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.6 Q8.1

Ex 9.6 Class 12 Maths Question 9.
x\frac { dy }{ dx } +y-x+xy\quad cotx=0(x\neq 0)
Solution:
x\frac { dy }{ dx } +y-x+xy\quad cotx=0
x\frac { dy }{ dx } +(1+xcot x)y=x
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.6 Q9.1

Ex 9.6 Class 12 Maths Question 10.
(x+y)\frac { dy }{ dx } =1
Solution:
(x+y)\frac { dy }{ dx } =1
\frac { 1 }{ (x+y) } \frac { dx }{ dy } =1\Rightarrow \frac { dx }{ dy } =x+y
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.6 Q10.1

Ex 9.6 Class 12 Maths Question 11.
ydx+(x-{ y }^{ 2 })dy=0
Solution:
ydx+(x-{ y }^{ 2 })dy=0
\Rightarrow y\frac { dx }{ dy } +x-{ y }^{ 2 }=0
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.6 Q11.1

Ex 9.6 Class 12 Maths Question 12.
\left( { x+3y }^{ 2 } \right) \frac { dy }{ dx } =y(y>0)
Solution:
y\frac { dx }{ dy } =x+{ 3y }^{ 2 }\quad or\quad \frac { dx }{ dy } -\frac { x }{ y } =3y
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.6 Q12.1

For each of the following Questions 13 to is find a particular solution, satisfying the given condition:

Ex 9.6 Class 12 Maths Question 13.
\frac { dy }{ dx } +2ytanx=sinx,y=0\quad when\quad x=\frac { \pi }{ 3 }
Solution:
\frac { dy }{ dx } +(2tanx)y=sinx,P=2tanx
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.6 Q13.1

Ex 9.6 Class 12 Maths Question 14.
\left( 1+{ x }^{ 2 } \right) \frac { dy }{ dx } +2xy=\frac { 1 }{ 1+{ x }^{ 2 } } ,y=0\quad when\quad x=1
Solution:
\frac { dy }{ dx } +\frac { 2x }{ 1+{ x }^{ 2 } } y=\frac { 1 }{ { \left( { 1+x }^{ 2 } \right) }^{ 2 } }
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.6 Q14.1

Ex 9.6 Class 12 Maths Question 15.
\frac { dy }{ dx } -3ycotx=sin2x,y=2\quad when\quad x=\frac { \pi }{ 2 }
Solution:
Here P = -3cot x
Q = sin 2x
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.6 Q15.1

Ex 9.6 Class 12 Maths Question 16.
Find the equation of the curve passing through the origin given that the slope of the tangent to the curve at any point (x,y) is equal to the sum of the coordinates of the point
Solution:
\frac { dy }{ dx } =x+y\Rightarrow \frac { dy }{ dx } -y=x\Rightarrow P=-1
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.6 Q16.1

Ex 9.6 Class 12 Maths Question 17.
Find the equation of the curve passing through the point (0, 2) given that the sum of the coordinates of any point on the curve exceeds the magnitude of the slope of the tangent to the curve at that point by 5
Solution:
By the given condition
x+y-\left| \frac { dy }{ dx } \right|=5
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.6 Q17.1
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.6 Q17.2

Ex 9.6 Class 12 Maths Question 18.
The integrating factor of the differential equation x\frac { dy }{ dx } -y={ 2x }^{ 2 }
(a) { e }^{ -x }
(b) { e }^{ -y }
(c) \frac { 1 }{ x }
(d) x
Solution:
(c) P=\frac { -1 }{ x } \therefore IF={ e }^{ -\int { \frac { 1 }{ x } dx } }={ e }^{ -logx }=\frac { 1 }{ x }

Ex 9.6 Class 12 Maths Question 19.
The integrating factor of the differential equation \left( { 1-y }^{ 2 } \right) \frac { dx }{ dy } +yx=ay(-1<y<1) is
(a) \frac { 1 }{ { y }^{ 2 }-1 }
(b) \frac { 1 }{ \sqrt { { y }^{ 2 }-1 } }
(c) \frac { 1 }{ 1-{ y }^{ 2 } }
(d) \frac { 1 }{ \sqrt { { 1-y }^{ 2 } } }
Solution:
(d) \left( { 1-y }^{ 2 } \right) \frac { dx }{ dy } +yx=ay
NCERT Solutions for Class 12 Maths Chapter 9 Differential Equations Ex 9.6 Q19.1

Read More

Class 12th Chapter -8 Application of Integrals | NCERT Maths Solution | NCERT Solution | Edugrown

It is important that you have a strong foundation in Maths Solutions. This can help you immensely in exams. Because there is no paper pattern set for the board exams. Every year there are different twists and turns in questions asked in board exams. While preparing for maths it becomes to go through every bit of detail. Thus, NCERT Solutions Class 12 Maths can help you lay a strong foundation. There solutions of each and every question given in the NCERT 12 Textbook in this article. There are crucial chapters like integration, algebra, and calculus which you can solve easily using these Class 12 Maths solutions. Using these NCERT Maths Class 12 Solutions can give you an edge over the other students.

NCERT Solutions for Class 12 Maths Chapter : 8 Application of Integrals

Ex 8.1 Class 12 Maths Question 1.
Find the area of the region bounded by the curve y² = x and the lines x = 1, x = 4, and the x-axis.
Solution:
The curve y² = x is a parabola with vertex at origin.Axis of x is the line of symmetry, which is the axis of parabola. The area of the region bounded by the curve, x = 1, x=4 and the x-axis. Area LMQP
NCERT Solutions for Class 12 Maths Chapter 8 Application of Integrals Ex 8.1 Q1.1

Ex 8.1 Class 12 Maths Question 2.
Find the area of the region bounded by y² = 9x, x = 2, x = 4 and x-axis in the first quadrant
Solution:
The given curve is y² = 9x, which is a parabola with vertex at (0, 0) and axis along x-axis. It is symmetrical about x-axis, as it contains only even powers of y. x = 2 and x = 4 are straight lines parallel toy-axis at a positive distance of 2 and 4 units from it respectively.
∴ Required area = Area ABCD
NCERT Solutions for Class 12 Maths Chapter 8 Application of Integrals Ex 8.1 Q2.1

Ex 8.1 Class 12 Maths Question 3.
Find the area of the region bounded by x² = 4y, y = 2, y = 4 and the y-axis in the first quadrant.
Solution:
The given curve x² = 4y is a parabola with vertex at (0,0). Also since it contains only even powers of x,it is symmetrical about y-axis.y = 2 and y = 4 are straight lines parallel to x-axis at a positive distance of 2 and 4 from it respectively.
NCERT Solutions for Class 12 Maths Chapter 8 Application of Integrals Ex 8.1 Q3.1

Ex 8.1 Class 12 Maths Question 4.
Find the area of the region bounded by the ellipse \frac { { x }^{ 2 } }{ 16 } +\frac { { y }^{ 2 } }{ 9 } =1
Solution:
The equation of the ellipse is \frac { { x }^{ 2 } }{ 16 } +\frac { { y }^{ 2 } }{ 9 } =1
The given ellipse is symmetrical about both axis as it contains only even powers of y and x.
NCERT Solutions for Class 12 Maths Chapter 8 Application of Integrals Ex 8.1 Q4.1

Ex 8.1 Class 12 Maths Question 5.
Find the area of the region bounded by the ellipse \frac { { x }^{ 2 } }{ 4 } +\frac { { y }^{ 2 } }{ 9 } =1
Solution:
\frac { { x }^{ 2 } }{ 4 } +\frac { { y }^{ 2 } }{ 9 } =1 It is an ellipse with centre (0,0) and length of major axis = 2a = 2×3 = 6 and length of minor axis = 2b = 2 × 2 = 4.
NCERT Solutions for Class 12 Maths Chapter 8 Application of Integrals Ex 8.1 Q5.1

Ex 8.1 Class 12 Maths Question 6.
Find the area of the region in the first quadrant enclosed by x-axis, line x = √3y and the circle x² + y² = 4. .
Solution:
Consider the two equations x² + y² = 4 … (i)
and x = √3y i.e. y=\frac { 1 }{ \sqrt { 3 } } x …(ii)
(1) x² + y² = 4 is a circle with centre O (0,0) and radius = 2.
NCERT Solutions for Class 12 Maths Chapter 8 Application of Integrals Ex 8.1 Q6.1

Ex 8.1 Class 12 Maths Question 7.
Find the area of the smaller part of the circle x² + y² = a² cut off by the line x=\frac { a }{ \sqrt { 2 } }
Solution:
The equation of the given curve are
x² + y² = a² …(i) and x=\frac { a }{ \sqrt { 2 } }  …(ii)
Clearly, (i) represent a circle and (ii) is the equation of a straight line parallel to y-axis at a
NCERT Solutions for Class 12 Maths Chapter 8 Application of Integrals Ex 8.1 Q7.1

Ex 8.1 Class 12 Maths Question 8.
The area between x = y² and x = 4 is divided into two equal parts by the line x = a, find the value of a.
Solution:
Graph of the curve x = y² is a parabola as given in the figure. Its vertex is O and axis is x-axis. QR is the ordinate along x = 4
NCERT Solutions for Class 12 Maths Chapter 8 Application of Integrals Ex 8.1 Q8.1

Ex 8.1 Class 12 Maths Question 9.
Find the area of the region bounded by the parabola y = x² and y = |x|.
Solution:
Clearly x² = y represents a parabola with vertex at (0, 0) positive direction of y-axis as its axis it opens upwards.
y = |x| i.e., y = x and y = -x represent two lines passing through the origin and making an angle of 45° and 135° with the positive direction of the x-axis.
The required region is the shaded region as shown in the figure. Since both the curve are symmetrical about y-axis. So,
Required area = 2 (shaded area in the first quadrant)
NCERT Solutions for Class 12 Maths Chapter 8 Application of Integrals Ex 8.1 Q9.1

Ex 8.1 Class 12 Maths Question 10.
Find the area bounded by the curve x² = 4y and the line x = 4y – 2
Solution:
Given curve is x² = 4y …(i)
which is an upward parabola with vertex at (0,0) and it is symmetrical about y-axis
Equation of the line is x = 4y – 2 …(ii)
Solving (i) and (ii) simultaneously, we get; (4y – 2)² = 4y
⇒ 16y² – 16y + 4 = 4y
⇒ 4y² – 5y + 1 = 0
NCERT Solutions for Class 12 Maths Chapter 8 Application of Integrals Ex 8.1 Q10.1
NCERT Solutions for Class 12 Maths Chapter 8 Application of Integrals Ex 8.1 Q10.2

Ex 8.1 Class 12 Maths Question 11.
Find the area of the region bounded by the curve y² = 4x and the line x = 3.
Solution:
The curve y² = 4x is a parabola as shown in the figure. Axis of the parabola is x-axis. The area of the region bounded by the curve y² = 4x and the line x = 3 is
A = Area of region OPQ = 2 (Area of the region OLQ)
NCERT Solutions for Class 12 Maths Chapter 8 Application of Integrals Ex 8.1 Q11.1

Choose the correct answer in the following Exercises 12 and 13:

Ex 8.1 Class 12 Maths Question 12.

Area lying in the first quadrant and bounded by the circle x² +

 y² = 4 and the lines x = 0 and x = 2 is

(a) π
(b) \frac { \pi }{ 2 }
(c) \frac { \pi }{ 3 }
(d) \frac { \pi }{ 4 }
Solution:
(a) x² + y² = 4. It is a circle at the centre (0,0) and r=2
NCERT Solutions for Class 12 Maths Chapter 8 Application of Integrals Ex 8.1 Q12.1

Ex 8.1 Class 12 Maths Question 13.
Area of the region bounded by the curve y² = 4x, y-axis and the line y = 3 is
(a) 2
(b) \frac { 9 }{ 4 }
(c) \frac { 9 }{ 3 }
(d) \frac { 9 }{ 2 }
Solution:
(b) y² = 4x is a parabola
NCERT Solutions for Class 12 Maths Chapter 8 Application of Integrals Ex 8.1 Q13.1

Ex 8.2 Class 12 Maths Question 1.
Find the area of the circle 4x² + 4y² = 9 which is interior to the parabola x² = 4y.
Solution:
Area is bounded by the circle 4x² + 4y² = 9 and interior of the parabola x² = 4y.
Putting x² = 4y in x² + y² = \frac { 9 }{ 4 }
We get 4y + y² = \frac { 9 }{ 4 }
NCERT Solutions for Class 12 Maths Chapter 8 Application of Integrals Ex 8.2 Q1.1

Ex 8.2 Class 12 Maths Question 2.
Find the area bounded by curves (x – 1)² + y² = 1 and x² + y² = 1.
Solution:
Given circles are x² + y² = 1 …(i)
and (x – 1)² + y² = 1 …(ii)
Centre of (i) is O (0,0) and radius = 1
NCERT Solutions for Class 12 Maths Chapter 8 Application of Integrals Ex 8.2 Q2.1
NCERT Solutions for Class 12 Maths Chapter 8 Application of Integrals Ex 8.2 Q2.2

Ex 8.2 Class 12 Maths Question 3.
Find the area of the region bounded by the curves y = x² + 2, y = x, x = 0 and x = 3.
Solution:
Equation of the parabola is y = x² + 2 or x² = (y – 2)
Its vertex is (0,2) axis is y-axis.
Boundary lines are y = x, x = 0, x = 3.
Graphs of the curve and lines have been shown in the figure.
Area of the region PQRO = Area of the region OAQR-Area of region OAP
NCERT Solutions for Class 12 Maths Chapter 8 Application of Integrals Ex 8.2 Q3.1

Ex 8.2 Class 12 Maths Question 4.
Using integration find the area of region bounded by the triangle whose vertices are (-1,0), (1,3) and (3,2).
Solution:
The points A (-1,0), B( 1,3) and C (3,2) are plotted and joined.
Area of ∆ABC = Area of ∆ ABL + Area of trap. BLMC – Area of ∆ACM …(i)
The equation of the line joining the points
NCERT Solutions for Class 12 Maths Chapter 8 Application of Integrals Ex 8.2 Q4.1

Ex 8.2 Class 12 Maths Question 5.
Using integration find the area of the triangular region whose sides have the equations y = 2x + 1,y = 3x + 1 and x = 4.
Solution:
The given lines are y = 2x + 1 …(i)
y = 3x + 1 …(ii)
x = 4 …(iii)
Subtract (i) from eq (ii) we get x = 0, Putting x = 0 in eq(i) y = 1
∴ Lines (ii) and (i) intersect at A (0,1) putting x = 4 in eq. (2) =>y = 12 + 1 = 13
The lines (ii) and (iii) intersect at B (4,13) putting x=4ineq. (i):y = 8 + 1 = 9
∴ Lines (i) and (ii); Intersect at C (4,9),
NCERT Solutions for Class 12 Maths Chapter 8 Application of Integrals Ex 8.2 Q5.1

Ex 8.2 Class 12 Maths Question 6.
Smaller area bounded by the circle x² + y² = 4 and the line x + y = 2
(a) 2 (π – 2)
(b) π – 2
(c) 2π – 1
(d) 2(π + 2)
Solution:
(b) A circle of radius 2 and centre at O is drawn.The line AB: x + y = 2 is passed through (2,0) and (0,2). Area of the region ACB
= Area of quadrant OAB – Area of ∆OAB …(i)
NCERT Solutions for Class 12 Maths Chapter 8 Application of Integrals Ex 8.2 Q6.1

Ex 8.2 Class 12 Maths Question 7.
Area lying between the curves y² = 4x and y = 2x.
(a) \frac { 2 }{ 3 }
(b) \frac { 1 }{ 3 }
(c) \frac { 1 }{ 4 }
(d) \frac { 3 }{ 4 }
Solution:
(b) The curve is y² = 4x …(1)
and the line is y = 2x …(2)
NCERT Solutions for Class 12 Maths Chapter 8 Application of Integrals Ex 8.2 Q7.1

Read More

Class 12th Chapter -7 Integrals | NCERT Maths Solution | NCERT Solution | Edugrown

It is important that you have a strong foundation in Maths Solutions. This can help you immensely in exams. Because there is no paper pattern set for the board exams. Every year there are different twists and turns in questions asked in board exams. While preparing for maths it becomes to go through every bit of detail. Thus, NCERT Solutions Class 12 Maths can help you lay a strong foundation. There solutions of each and every question given in the NCERT 12 Textbook in this article. There are crucial chapters like integration, algebra, and calculus which you can solve easily using these Class 12 Maths solutions. Using these NCERT Maths Class 12 Solutions can give you an edge over the other students.

NCERT Solutions for Class 12 Maths Chapter : 7 Integrals

Find an antiderivative (or integral) of the following by the method of inspection:

Ex 7.1 Class 12 Maths Question 1.
sin 2x
Solution:
\int { sin2x\quad dx=-\frac { cos2x }{ 2 } +C }

Ex 7.1 Class 12 Maths Question 2.
cos 3x
Solution:
\int { cos3x\quad dx=\frac { sin3x }{ 3 } +C }

Ex 7.1 Class 12 Maths Question 3.
{ e }^{ 2x }
Solution:
\int { { e }^{ 2x }dx=\frac { { e }^{ 2x } }{ 2 } +C }

Ex 7.1 Class 12 Maths Question 4.
(ax + c)²
Solution:
\int { { (ax+b) }^{ 2 }dx=\frac { { (ax+b) }^{ 3 } }{ 3a } } +C

Ex 7.1 Class 12 Maths Question 5.
{ sin\quad 2x-4e }^{ 3x }
Solution:
\int { \left( { sin2x-4e }^{ 3x } \right) dx=-\frac { cos2x }{ 2 } -\frac { { 4e }^{ 3x } }{ 3 } +C }

Find the following integrals in Exercises 6 to 20 :

Ex 7.1 Class 12 Maths Question 6.
\int { \left( { 4e }^{ 3x }+1 \right) dx }
Solution:
=\int { { 4e }^{ 3x }dx+\int { dx=\frac { 4 }{ 3 } { e }^{ 3x }+x+c } }

Ex 7.1 Class 12 Maths Question 7.
\int { { x }^{ 2 }\left( 1-\frac { 1 }{ { x }^{ 2 } } \right) dx }
Solution:
=\int { { x }^{ 2 }\left( 1-\frac { 1 }{ { x }^{ 2 } } \right) dx } =\frac { { x }^{ 3 } }{ 3 } -x+C

Ex 7.1 Class 12 Maths Question 8.
\int { { (ax }^{ 2 }+bx+c)dx }
Solution:
=\frac { { ax }^{ 3 } }{ 3 } +\frac { { bx }^{ 2 } }{ 2 } +cx+d

Ex 7.1 Class 12 Maths Question 9.
\int { \left( { 2x }^{ 2 }+{ e }^{ x } \right) dx }
Solution:
=\frac { { 2x }^{ 3 } }{ 3 } +{ e }^{ x }+c

Ex 7.1 Class 12 Maths Question 10.
\int { { \left[ \sqrt { x } -\frac { 1 }{ \sqrt { x } } \right] }^{ 2 }dx }
Solution:
=\frac { { x }^{ 2 } }{ 2 } +logx-2x+C

Ex 7.1 Class 12 Maths Question 11.
\int { \frac { { x }^{ 3 }+{ 5x }^{ 2 }-4 }{ { x }^{ 2 } } dx }
Solution:
\int { \left( \frac { { x }^{ 3 } }{ { x }^{ 2 } } +\frac { { 5x }^{ 2 } }{ { x }^{ 2 } } -\frac { 4 }{ { x }^{ 2 } } \right) }
=\int { xdx+5\int { 1dx-4 } \int { { x }^{ 2 }dx } }
=\frac { { x }^{ 2 } }{ 2 } +5x+\frac { 4 }{ x } +c

Ex 7.1 Class 12 Maths Question 12.
\int { \frac { { x }^{ 3 }+3x+4 }{ \sqrt { x } } dx }
Solution:
=\int { \left( { x }^{ \frac { 5 }{ 2 } }+{ 3x }^{ \frac { 1 }{ 2 } }+4{ x }^{ -\frac { 1 }{ 2 } } \right) } dx
=\frac { 2 }{ 7 } { x }^{ \frac { 7 }{ 2 } }+{ 2x }^{ \frac { 3 }{ 2 } }+8\sqrt { x } +c

Ex 7.1 Class 12 Maths Question 13.
\int { \frac { { x }^{ 3 }-{ x }^{ 2 }+x-1 }{ x-1 } dx }
Solution:
=\int { \frac { { x }^{ 2 }(x-1)+(x-1) }{ x-1 } dx }
=\int { \left( { x }^{ 2 }+1 \right) dx } =\frac { { x }^{ 3 } }{ 3 } +x+c

Ex 7.1 Class 12 Maths Question 14.
\int { \left( 1-x \right) \sqrt { x } dx }
Solution:
=\int { { x }^{ \frac { 1 }{ 2 } }-{ x }^{ \frac { 3 }{ 2 } }dx\quad =\quad \frac { 2 }{ 3 } { x }^{ \frac { 3 }{ 2 } }-\frac { 2 }{ 5 } { x }^{ \frac { 5 }{ 2 } } }

Ex 7.1 Class 12 Maths Question 15.
\int { \sqrt { x } \left( { 3x }^{ 2 }+2x+3 \right) dx }
Solution:
=\int { \left( { 3x }^{ \frac { 5 }{ 2 } }+{ 2 }^{ \frac { 3 }{ 2 } }+{ 3x }^{ \frac { 1 }{ 2 } } \right) dx }
=\frac { 6 }{ 7 } { x }^{ \frac { 7 }{ 2 } }+\frac { 4 }{ 5 } { x }^{ \frac { 5 }{ 2 } }+\frac { 6 }{ 3 } { x }^{ \frac { 3 }{ 2 } }+c

Ex 7.1 Class 12 Maths Question 16.
\int { (2x-3cosx+{ e }^{ x })dx }
Solution:
=\frac { { 2x }^{ 2 } }{ 2 } -3sinx+{ e }^{ x }+c
={ x }^{ 2 }-3sinx+{ e }^{ x }+c

Ex 7.1 Class 12 Maths Question 17.
\int { \left( { 2x }^{ 2 }-3sinx+5\sqrt { x } \right) dx }
Solution:
=\frac { { 2x }^{ 3 } }{ 3 } +3cosx+5\frac { { x }^{ \frac { 3 }{ 2 } } }{ \frac { 3 }{ 2 } } +c
=\frac { 2 }{ 3 } { x }^{ 3 }+3cosx+\frac { 10 }{ 3 } { x }^{ \frac { 3 }{ 2 } }+c

Ex 7.1 Class 12 Maths Question 18.
\int { secx(secx+tanx)dx }
Solution:
=\int { { (sec }^{ 2 }x+secxtanx)dx }
= tanx + secx + c

Ex 7.1 Class 12 Maths Question 19.
\int { \frac { { sec }^{ 2 }x }{ { cosec }^{ 2 }x } dx }
Solution:
=\int { \frac { 1 }{ { cos }^{ 2 }x } } { sin }^{ 2 }xdx
=\int { tan } ^{ 2 }xdx\quad =\int { { (sec }^{ 2 }x-1)dx\quad =tanx-x+c }

Ex 7.1 Class 12 Maths Question 20.
\int { \frac { 2-3sinx }{ { cos }^{ 2 }x } dx }
Solution:
=\int { \left( \frac { 2 }{ { cos }^{ 2 }x } -3\frac { sinx }{ { cos }^{ 2 }x } \right) dx }
=\int { ({ 2sec }^{ 2 }x-3secxtanx)dx }
= 2tanx – 3secx + c

Choose the correct answer in Exercises 21 and 22.

Ex 7.1 Class 12 Maths Question 21.
The antiderivative \left( \sqrt { x } +\frac { 1 }{ \sqrt { x } } \right)  equals
(a) \frac { 1 }{ 3 } { x }^{ \frac { 1 }{ 3 } }+{ 2x }^{ \frac { 1 }{ 2 } }+c
(b) \frac { 2 }{ 3 } { x }^{ \frac { 2 }{ 3 } }+{ \frac { 1 }{ 2 } x }^{ 2 }+c
(c) \frac { 2 }{ 3 } { x }^{ \frac { 3 }{ 2 } }+{ 2x }^{ \frac { 1 }{ 2 } }+c
(d) \frac { 3 }{ 2 } { x }^{ \frac { 3 }{ 2 } }+\frac { 1 }{ 2 } { x }^{ \frac { 1 }{ 2 } }+c
Solution:
(c) \int { \left( \sqrt { x } +\frac { 1 }{ \sqrt { x } } \right) dx }
=\int { \left( { x }^{ \frac { 1 }{ 2 } }+{ x }^{ \frac { 1 }{ 2 } } \right) dx }
=\frac { 2 }{ 3 } { x }^{ \frac { 3 }{ 2 } }+{ 2x }^{ \frac { 1 }{ 2 } }+c

Ex 7.1 Class 12 Maths Question 22.
If \frac { d }{ dx } f(x)={ 4x }^{ 3 }-\frac { 3 }{ { x }^{ 4 } }  such that f(2)=0 then f(x) is
(a) { x }^{ 4 }+\frac { 1 }{ { x }^{ 3 } } -\frac { 129 }{ 8 }
(b) { x }^{ 3 }+\frac { 1 }{ { x }^{ 4 } } +\frac { 129 }{ 8 }
(c) { x }^{ 4 }+\frac { 1 }{ { x }^{ 3 } } +\frac { 129 }{ 8 }
(d) { x }^{ 3 }+\frac { 1 }{ { x }^{ 4 } } -\frac { 129 }{ 8 }
Solution:
(a) f(x)=\int { \left( { 4x }^{ 3 }-\frac { 3 }{ { x }^{ 4 } } \right) dx }
={ x }^{ 4 }+\frac { 1 }{ { x }^{ 3 } } +c
\therefore f(2)={ (2) }^{ 4 }+\frac { 1 }{ { (2) }^{ 3 } } +c=0=-\frac { 129 }{ 8 }

Integrate the functions in Exercises 1 to 37:

Ex 7.1 Class 12 Maths Question 1.
\frac { 2x }{ 1+{ x }^{ 2 } }
Solution:
Let 1+x² = t
⇒ 2xdx = dt
\therefore \int { \frac { 2x }{ 1+{ x }^{ 2 } } dx\quad = } \int { \frac { dt }{ t } \quad =logt+C\quad =log(1+{ x }^{ 2 })+C }

Ex 7.2 Class 12 Maths Question 2.
\frac { { \left( logx \right) }^{ 2 } }{ x }
Solution:
Let logx = t
⇒ \frac { 1 }{ x }dx=dt
\therefore \int { \frac { { (logx) }^{ 2 } }{ x } dx } \quad =\int { { t }^{ 2 }dt } \quad =\frac { { t }^{ 3 } }{ 3 } +c\quad =\frac { 1 }{ 3 } { (logx) }^{ 3 }+c

Ex 7.2 Class 12 Maths Question 3.
\frac { 1 }{ x+xlogx }
Solution:
Put 1+logx = t
∴ \frac { 1 }{ x }dx=dt
\int { \frac { 1 }{ x(1+logx) } dx } =\int { \frac { 1 }{ t } dt } =log|t|+c
= log|1+logx|+c

Ex 7.2 Class 12 Maths Question 4.
sinx sin(cosx)
Solution:
Put cosx = t, -sinx dx = dt
\int { sinx\quad sin(cosx)dx } =-\int { sin(cosx) } (-sinx)dx
=-\int { sint\quad dt } \quad =cost+c\quad =cos(cosx)+c

Ex 7.2 Class 12 Maths Question 5.
sin(ax+b) cos(ax+b)
Solution:
let sin(ax+b) = t
⇒ cos(ax+b)dx = dt
\therefore \int { sin(ax+b)cos(ax+b)dx } =\frac { 1 }{ a } \int { t\quad dt }
=\frac { 1 }{ a } .\frac { { t }^{ 2 } }{ 2 } +c\quad =\frac { 1 }{ 2a } { sin }^{ 2 }(ax+b)+C

Ex 7.2 Class 12 Maths Question 6.
\sqrt { ax+b }
Solution:
\int { \sqrt { ax+b } dx } \quad =\frac { 2 }{ 3a } { (ax+b) }^{ \frac { 3 }{ 2 } }+C

Ex 7.2 Class 12 Maths Question 7.
x\sqrt { x+2 }
Solution:
Let x+2 = t²
⇒ dx = 2t dt
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.2 Q7.1

Ex 7.2 Class 12 Maths Question 8.
x\sqrt { 1+{ 2x }^{ 2 } }
Solution:
let 1+2x² = t²
⇒ 4x dx = 2t dt
x\quad dx=\frac { t }{ 2 } dt\int { x\sqrt { 1+{ 2x }^{ 2 } } dx }
=\frac { 1 }{ 2 } \int { { t }^{ 2 }dt } =\frac { { t }^{ 3 } }{ 6 } +c=\frac { 1 }{ 6 } { ({ 1+2x }^{ 2 }) }^{ \frac { 3 }{ 2 } }+c

Ex 7.2 Class 12 Maths Question 9.
(4x+2)\sqrt { { x }^{ 2 }+x+1 }
Solution:
let x²+x+1 = t
⇒(2x+1)dx = dt
\therefore \int { (4x+1)\sqrt { { x }^{ 2 }+x+1 } dx } =2\int { \sqrt { t } dt }
=\frac { { 2t }^{ \frac { 3 }{ 2 } } }{ ^{ \frac { 3 }{ 2 } } } +c\quad =\frac { 4 }{ 3 } { t }^{ \frac { 3 }{ 2 } }+c\quad =\frac { 4 }{ 3 } { ({ x }^{ 2 }+x+1) }^{ \frac { 3 }{ 2 } }+c

Ex 7.2 Class 12 Maths Question 10.
\frac { 1 }{ x-\sqrt { x } }
Solution:
\int { \frac { 1 }{ x-\sqrt { x } } dx } =\int { \frac { 1 }{ \sqrt { x } (\sqrt { x-1 } ) } dx } =I
Let √x-1 = t
\frac { 1 }{ 2 } { x }^{ -\frac { 1 }{ 2 } }dx=dt
I=2\int { \frac { dt }{ t } }
= 2logt + c
= 2log(√x-1)+c

Ex 7.2 Class 12 Maths Question 11.
\frac { x }{ \sqrt { x+4 } } ,x>0
Solution:
let x+4 = t
⇒ dx = dt, x = t-4
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.2 Q11.1

Ex 7.2 Class 12 Maths Question 12.
{ { (x }^{ 3 }-1) }^{ \frac { 1 }{ 3 } }.{ x }^{ 5 }
Solution:
\int { { { (x }^{ 3 }-1) }^{ \frac { 1 }{ 3 } }.{ x }^{ 5 }.dx } \quad =\frac { 1 }{ 7 } { { (x }^{ 3 }-1) }^{ \frac { 7 }{ 3 } }+\frac { 1 }{ 4 } { { (x }^{ 3 }-1) }^{ \frac { 4 }{ 3 } }+c

Ex 7.2 Class 12 Maths Question 13.
\frac { { x }^{ 2 } }{ { { (2+3x }^{ 3 }) }^{ 3 } }
Solution:
Let 2+3x³ = t
⇒ 9x² dx = dt
\therefore \int { \frac { { x }^{ 2 } }{ { { (2+3x }^{ 3 }) }^{ 3 } } dx } =\frac { 1 }{ 9 } \int { \frac { dt }{ { t }^{ 3 } } =\frac { 1 }{ 9 } \int { { t }^{ -3 }dt } }
=-\frac { 1 }{ { 18t }^{ 2 } } +c\quad =-\frac { 1 }{ 18(2+{ 3x }^{ 3 })^{ 2 } } +c

Ex 7.2 Class 12 Maths Question 14.
\frac { 1 }{ x(logx)^{ m } } ,x>0
Solution:
Put log x = t, so that \frac { 1 }{ x }dx=dt
\therefore \int { \frac { 1 }{ { x(logx) }^{ m } } dx } =\int { \frac { dt }{ { t }^{ m } } =\frac { { t }^{ -m+1 } }{ -m+1 } +c }
=\frac { { (logx) }^{ 1-m } }{ 1-m } +c

Ex 7.2 Class 12 Maths Question 15.
\frac { x }{ 9-4{ x }^{ 2 } }
Solution:
put 9-4x² = t, so that -8x dx = dt
\therefore \int { \frac { x }{ 9-{ 4x }^{ 2 } } dx } =-\frac { 1 }{ 8 } \int { \frac { dt }{ t } } =-\frac { 1 }{ 8 } log|t|+c
=\frac { 1 }{ 8 } log\frac { 1 }{ |9-{ 4x }^{ 2 }| } +c

Ex 7.2 Class 12 Maths Question 16.
{ e }^{ 2x+3 }
Solution:
put 2x+3 = t
so that 2dx = dt
\int { { e }^{ 2x+3 } } dx\quad =\frac { 1 }{ 2 } \int { { e }^{ t }dt } \quad =\frac { 1 }{ 2 } { e }^{ t }+c\quad =\frac { 1 }{ 2 } { e }^{ 2x+3 }+c

Ex 7.2 Class 12 Maths Question 17.
\frac { x }{ { e }^{ { x }^{ 2 } } }
Solution:
Let x² = t
⇒ 2xdx = dt ⇒ xdx=\frac { dt }{ 2 }
\therefore \int { \frac { x }{ { e }^{ { x }^{ 2 } } } dx } \quad =\frac { 1 }{ 2 } \int { \frac { dt }{ { e }^{ t } } \quad =\frac { 1 }{ 2 } \int { { e }^{ -t } } dt }
=-\frac { 1 }{ 2 } { e }^{ { -x }^{ 2 } }+c

Ex 7.2 Class 12 Maths Question 18.
\frac { { e }^{ { tan }^{ -1 }x } }{ 1+{ x }^{ 2 } }
Solution:
let\quad { tan }^{ -1 }x=t\Rightarrow \frac { 1 }{ 1+{ x }^{ 2 } } dx=dt
\therefore \int { \frac { { e }^{ { tan }^{ -1 }x } }{ 1+{ x }^{ 2 } } dx } \quad =\int { { e }^{ t }dt\quad ={ e }^{ { tan }^{ -1 }x }+c }

Ex 7.2 Class 12 Maths Question 19.
\frac { { e }^{ 2x }-1 }{ { e }^{ 2x }+1 }
Solution:
\int { \frac { { e }^{ 2x }-1 }{ { e }^{ 2x }+1 } dx\quad =\int { \frac { { e }^{ x }({ e }^{ x }-{ e }^{ -x }) }{ { e }^{ x }({ e }^{ x }+{ e }^{ -x }) } dx=I } }
put ex+e-x = t
so that (ex-e-x)dx = dt
\therefore I=\int { \frac { dt }{ t } =log|t|+c } =log|{ e }^{ x }+{ e }^{ -x }|+c

Ex 7.2 Class 12 Maths Question 20.
\frac { { e }^{ 2x }-{ e }^{ 2x } }{ { e }^{ 2x }+{ e }^{ -2x } }
Solution:
put e2x-e-2x = t
so that (2e2x-2e-2x)dx = dt
\therefore \int { \frac { { e }^{ 2x }-{ e }^{ 2x } }{ { e }^{ 2x }+{ e }^{ -2x } } } dx=\frac { 1 }{ 2 } \int { \frac { 1 }{ t } dt } =\frac { 1 }{ 2 } log|t|+c
=\frac { 1 }{ 2 } log+|{ e }^{ 2x }+{ e }^{ -2x }|+c

Ex 7.2 Class 12 Maths Question 21.
tan²(2x-3)
Solution:
∫tan²(2x-3)dx = ∫[sec²(2x-3)-1]dx = I
put 2x-3 = t
so that 2dx = dt
I = \frac { 1 }{ 2 } ∫sec²t dt-x+c
\frac { 1 }{ 2 }t-x+c
\frac { 1 }{ 2 }tan(2x-3)-x+c

Ex 7.2 Class 12 Maths Question 22.
sec²(7-4x)
Solution:
∫sec²(7-4x)dx
\frac { tan(7-4x) }{ -4 }+c

Ex 7.2 Class 12 Maths Question 23.
\frac { { sin }^{ -1 }x }{ \sqrt { 1-{ x }^{ 2 } } }
Solution:
let\quad { sin }^{ -1 }x=t\quad \Rightarrow \frac { 1dx }{ \sqrt { 1-{ x }^{ 2 } } } =dt
\int { \frac { { sin }^{ -1 }x }{ \sqrt { 1-{ x }^{ 2 } } } dx } =\int { t\quad dt } =\frac { 1 }{ 2 } { t }^{ 2 }+c=\frac { 1 }{ 2 } { { (sin }^{ -1 }x) }^{ 2 }+c

Ex 7.2 Class 12 Maths Question 24.
\frac { 2cosx-3sinx }{ 6cosx+4sinx }
Solution:
put 2sinx+4cosx = t
⇒ (2cosx-3sinx)dx = dt
\frac { 1 }{ 2 } \int { \frac { 2cosx-3sinx }{ 2sinx+3cosx } dx } =\frac { 1 }{ 2 } \int { \frac { dt }{ t } } =\frac { 1 }{ 2 } log|t|+c
\frac { 1 }{ 2 } log|2sinx+3cosx|+c

Ex 7.2 Class 12 Maths Question 25.
\frac { 1 }{ { cos }^{ 2 }x{ (1-tanx) }^{ 2 } }
Solution:
put 1-tanx = t
so that -sec²x dx = dt
\therefore \int { \frac { 1 }{ { cos }^{ 2 }x{ (1-tanx) }^{ 2 } } dx } =\int { \frac { { sec }^{ 2 }x }{ { (1-tanx) }^{ 2 } } dx }
=-\int { \frac { dt }{ { t }^{ 2 } } } =\frac { 1 }{ t } +c=\frac { 1 }{ (1-tanx) } +c

Ex 7.2 Class 12 Maths Question 26.
\frac { cos\sqrt { x } }{ \sqrt { x } }
Solution:
put\quad \sqrt { x } =t,so\quad that\frac { 1 }{ 2\sqrt { x } } dx=dt
\therefore \int { \frac { cos\sqrt { x } }{ \sqrt { x } } } dx\quad =\quad 2\quad =\int { cost\quad dt\quad = } 2sint+c
= 2sin√x+c

Ex 7.2 Class 12 Maths Question 27.
\sqrt { sin2x } cos2x
Solution:
put sin2x = t²
⇒ cos2x dx = t dt
\therefore \int { \sqrt { sin2x } .cos2x\quad dx } \quad =\int { t.tdt=\frac { { t }^{ 3 } }{ 3 } +c }
=\frac { { (sin2x) }^{ \frac { 3 }{ 2 } } }{ 3 } +c

Ex 7.2 Class 12 Maths Question 28.
\frac { cosx }{ \sqrt { 1+sinx } }
Solution:
put 1+sinx = t²
⇒cosx dx = 2t dt
\therefore \int { \frac { cosx }{ \sqrt { 1+sinx } } dx } =2\int { dt } =2t+c
=2\sqrt { 1+sinx } +c

Ex 7.2 Class 12 Maths Question 29.
cotx log sinx
Solution:
put log sinx = t,
⇒ cot x dx = dt
\therefore \int { cot\quad logsinx\quad dx } =\int { t } dt\quad =\frac { { t }^{ 2 } }{ 2 } +c
=\frac { 1 }{ 2 } { (log\quad sinx) }^{ 2 }+c

Ex 7.2 Class 12 Maths Question 30.
\frac { sinx }{ 1+cosx }
Solution:
put 1+cosx = t
⇒ -sinx dx = dt
\therefore \int { \frac { sinx }{ 1+cosx } dx } =\int { -\frac { dt }{ t } } =-logt+c
=-log(1+cosx)+c

Ex 7.2 Class 12 Maths Question 31.
\frac { sinx }{ { (1+cosx) }^{ 2 } }
Solution:
put 1+cosx = t
so that -sinx dx = dt
\therefore \int { \frac { sinx }{ { (1+cosx) }^{ 2 } } dx } =-\int { \frac { dt }{ { t }^{ 2 } } }
=\frac { 1 }{ t } +c=\frac { 1 }{ 1+cosx } +c

Ex 7.2 Class 12 Maths Question 32.
\frac { 1 }{ 1+cotx }
Solution:
\int { \frac { 1 }{ 1+\frac { cosx }{ sinx } } } dx=\frac { 1 }{ 2 } \int { \frac { 2sinx\quad dx }{ sinx+cosx } }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.2 Q32.1

Ex 7.2 Class 12 Maths Question 33.
\frac { 1 }{ 1-tanx }
Solution:
\int { \frac { 1 }{ 1-tanx } } dx=\frac { 1 }{ 2 } \int { \frac { 2cosx\quad dx }{ cosx-sinx } }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.2 Q33.1

Ex 7.2 Class 12 Maths Question 34.
\frac { \sqrt { tanx } }{ sinxcosx }
Solution:
\int { \frac { \sqrt { tanx } }{ sinxcosx } dx } =\int { \frac { \sqrt { tanx } }{ tanx } } .{ sec }^{ 2 }xdx
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.2 Q34.1

Ex 7.2 Class 12 Maths Question 35.
\frac { { (1+logx) }^{ 2 } }{ x }
Solution:
let 1+logx = t
⇒ \frac { 1 }{ x }dx=dt
\int { \frac { { (1+logx) }^{ 2 } }{ x } dx } =\int { { t }^{ 2 }dt } =\frac { { t }^{ 3 } }{ 3 } +c
=\frac { 1 }{ 3 } { (1+logx) }^{ 3 }+c

Ex 7.2 Class 12 Maths Question 36.
\frac { (x+1){ (x+logx) }^{ 2 } }{ x }
Solution:
put x+logx = t
\left( \frac { x+1 }{ x } \right) dx=dt
\therefore \int { \frac { { (x+1)(x+logx) }^{ 2 } }{ x } } dx=\int { { t }^{ 2 }dt }
=\frac { { (x+logx) }^{ 3 } }{ 3 } +c

Ex 7.2 Class 12 Maths Question 37.
\frac { { x }^{ 3 }sin({ tan }^{ -1 }{ x }^{ 4 }) }{ 1+{ x }^{ 8 } } dx
Solution:
put\quad { tan }^{ -1 }{ x }^{ 4 }=t\quad so\quad that\frac { 1 }{ 1+{ x }^{ 8 } } .{ 4x }^{ 3 }dx=dt
\therefore \int { \frac { { x }^{ 3 }sin({ tan }^{ -1 }{ x }^{ 4 }) }{ 1+{ x }^{ 8 } } } dx=\frac { 1 }{ 4 } \int { sint\quad dt }
=\frac { 1 }{ 4 } (-cost)+c=-\frac { 1 }{ 4 } cos({ tan }^{ -1 }{ x }^{ 4 })+c

Choose the correct answer in exercises 38 and 39

Ex 7.2 Class 12 Maths Question 38.
\int { \frac { { 10x }^{ 9 }+{ 10 }^{ x }log{ e }^{ 10 } }{ { x }^{ 10 }+{ 10 }^{ x } } dx }
(a) 10x – x10 + C
(b) 10x + x10 + C
(c) (10x – x10) + C
(d) log (10x + x10) + C
Solution:
(d) \int { \frac { { 10x }^{ 9 }+{ 10 }^{ x }log{ e }^{ 10 } }{ { x }^{ 10 }+{ 10 }^{ x } } dx }
= log (10x + x10) + C

Ex 7.2 Class 12 Maths Question 39.
\int { \frac { dx }{ { sin }^{ 2 }x{ \quad cos }^{ 2 }x } = }
(a) tanx + cotx + c
(b) tanx – cotx + c
(c) tanx cotx + c
(d) tanx – cot2x + c
Solution:
(c) \int { \frac { dx }{ { sin }^{ 2 }x{ \quad cos }^{ 2 }x } = }
=\int { \left( { sec }^{ 2 }x+{ cosec }^{ 2 }x \right) dx }
= tanx – cotx + c

Find the integrals of the functions in Exercises 1 to 22.

Ex 7.3 Class 12 Maths Question 1.
sin²(2x+5)
Solution:
∫sin²(2x+5)dx
\frac { 1 }{ 2 }∫[1-cos2(2x+5)]dx
\frac { 1 }{ 2 }∫[1-cos(4x+10)]dx
\frac { 1 }{ 2 } \left[ x-\frac { sin(4x+10) }{ 4 } \right] +c

Ex 7.3 Class 12 Maths Question 2.
sin3x cos4x
Solution:
∫sin3x cos4x
\frac { 1 }{ 2 }∫[sin(3x+4x)+cos(3x-4x)]dx
\frac { 1 }{ 2 }∫[sin7x+sin(-x)]dx
-\frac { 1 }{ 14 } cos7x+\frac { 1 }{ 2 } cosx+c

Ex 7.3 Class 12 Maths Question 3.
∫cos2x cos4x cos6x dx
Solution:
\frac { 1 }{ 2 } ∫cos2x cos4x cos6x dx
\frac { 1 }{ 2 } ∫(cos6x+cos2x) cos6x dx
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.3 Q3.1

Ex 7.3 Class 12 Maths Question 4.
∫sin3(2x+1)dx
Solution:
\frac { 1 }{ 4 } ∫[3sin(2x+1)-sin3(2x+1)]dx
-\frac { 3 }{ 8 } cos(2x+1)+\frac { 1 }{ 24 } [4{ cos }^{ 3 }(2x+1)-3cos(2x+1)]+c
-\frac { 1 }{ 2 } cos(2x+1)+\frac { 1 }{ 6 } { cos }^{ 3 }(2x+1)+c

Ex 7.3 Class 12 Maths Question 5.
sin3x cos3x
Solution:
put sin x = t
⇒ cos x dx = dt
\therefore \int { { sin }^{ 3 }x{ cos }^{ 3 }xdx } =\int { { t }^{ 3 }(1-{ t }^{ 2 })dt }
\frac { { t }^{ 4 } }{ 4 } -\frac { { t }^{ 6 } }{ 6 } +c=\frac { { (sinx) }^{ 4 } }{ 4 } -\frac { { (sinx) }^{ 6 } }{ 6 } +c

Ex 7.3 Class 12 Maths Question 6.
sinx sin2x sin3x
Solution:
∫sinx sin2x sin3x dx
\frac { 1 }{ 2 } ∫ 2sin x sin 2x sin 3x dx
\frac { 1 }{ 2 } ∫ (cosx – cos3x)sin 3x dx
\frac { 1 }{ 2 } ∫ (sin 4x + sin 2x – sin 6x)dx
\frac { 1 }{ 4 } \left\{ \frac { -cos4x }{ 4 } -\frac { cos2x }{ 2 } +\frac { cos6x }{ 6 } \right\} +c

Ex 7.3 Class 12 Maths Question 7.
sin 4x sin 8x
Solution:
\frac { 1 }{ 2 }∫sin 4x sin 8xdx
\frac { 1 }{ 2 }∫(cos 4x – cos 12x)dx
\frac { 1 }{ 2 } \left[ \frac { sin4x }{ 4 } -\frac { sin12x }{ 12 } \right] +c

Ex 7.3 Class 12 Maths Question 8.
\frac { 1-cosx }{ 1+cosx }
Solution:
\int { \frac { 1-cosx }{ 1+cosx } dx }
\int { \frac { { 2sin }^{ 2 }\frac { x }{ 2 } }{ { 2cos }^{ 2 }\frac { x }{ 2 } } dx } =\int { { tan }^{ 2 }\frac { x }{ 2 } dx }
=\int { \left[ { sec }^{ 2 }\frac { x }{ 2 } -1 \right] } dx\quad =2tan\frac { x }{ 2 } -x+c

Ex 7.3 Class 12 Maths Question 9.
\frac { cosx }{ 1+cosx }
Solution:
\int { \frac { cosx }{ 1+cosx } dx }
=\int { 1 } dx-\int { \frac { 1 }{ 1+cosx } dx }
=x-\frac { 1 }{ 2 } \int { { sec }^{ 2 }\frac { x }{ 2 } dx+c\quad =x-tan\frac { x }{ 2 } +c }

Ex 7.3 Class 12 Maths Question 10.
∫sinx4 dx
Solution:
\int { { (\frac { 1-cos2x }{ 2 } ) }^{ 2 }dx } \quad =\frac { 1 }{ 4 } \int { \left( { 1+cos }^{ 2 }2x-2cos2x \right) dx }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.3 Q10.1

Ex 7.3 Class 12 Maths Question 11.
cos4 2x
Solution:
∫ cos4 2x dx
\int { { \left( \frac { 1+cos4x }{ 2 } \right) }^{ 2 } } dx
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.3 Q11.1

Ex 7.3 Class 12 Maths Question 12.
\frac { { sin }^{ 2 }x }{ 1+cosx }
Solution:
\int { \frac { { sin }^{ 2 }x }{ 1+cosx } } dx\quad =\int { \frac { 1-{ cos }^{ 2 }x }{ 1+cosx } } dx
\int { (1-cosx) } dx\quad =x-sinx+c

Ex 7.3 Class 12 Maths Question 13.
\frac { cos2x-cos2\alpha }{ cosx-cos\alpha }
Solution:
let I = \int { \frac { \left( { 2cos }^{ 2 }x-1 \right) -\left( { 2cos }^{ 2 }\alpha -1 \right) }{ cosx-cos\alpha } } dx
\int { \frac { 2\left( { cos }x-cos\alpha \right) -\left( { cos }x+cos\alpha \right) }{ cosx-cos\alpha } } dx
= 2∫cos x dx + 2cos α∫dx
= 2(sinx+xcosα)+c

Ex 7.3 Class 12 Maths Question 14.
\frac { cosx-sinx }{ 1+sin2x }
Solution:
let I = \int { \frac { cosx-sinx }{ 1+sin2x } } dx=\int { \frac { cosx-sinx }{ { (cosx+sinx) }^{ 2 } } dx }
put cosx+sinx = t
⇒ (-sinx+cosx)dx = dt
I=\int { \frac { dt }{ { t }^{ 2 } } } =-\frac { 1 }{ t } +c\quad =\frac { -1 }{ cosx+sinx } +c

Ex 7.3 Class 12 Maths Question 15.
\int { { tan }^{ 3 }2x\quad sec2x\quad dx=I }
Solution:
I = ∫(sec22x-1)sec2x tan 2xdx
put sec2x=t,2 sec2x tan2x dx=dt
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.3 Q15.1

Ex 7.3 Class 12 Maths Question 16.
tan4x
Solution:
let I = ∫tan4 dx
= ∫(sec²x-1)²dx
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.3 Q16.1
Ex 7.3 Class 12 Maths Question 17.
\frac { { sin }^{ 3 }x+{ cos }^{ 3 }x }{ { sin }^{ 2 }x{ cos }^{ 2 }x }
Solution:
\int { \left( \frac { { sin }^{ 3 }x }{ { sin }^{ 2 }x{ cos }^{ 2 }x } +\frac { { cos }^{ 2 }x }{ sinx{ cos }^{ 2 }x } \right) dx }
= secx-cosecx+c

Ex 7.3 Class 12 Maths Question 18.
\frac { cos2x+{ 2sin }^{ 2 }x }{ { cos }^{ 2 }x }
Solution:
I=\int { \frac { \left( { cos }^{ 2 }x-{ sin }^{ 2 }x \right) +2{ sin }^{ 2 }x }{ { cos }^{ 2 }x } } dx
=\int { \frac { \left( { cos }^{ 2 }x-{ sin }^{ 2 }x \right) }{ { cos }^{ 2 }x } } dx\quad =\int { { sec }^{ 2 }xdx\quad =tanx+c }

Ex 7.3 Class 12 Maths Question 19.
\frac { 1 }{ sinx{ cos }^{ 3 }x }
Solution:
I=\int { \left( tanx+\frac { 1 }{ tanx } \right) } { sec }^{ 2 }xdx
put tanx = t
so that sec²x dx = dt
I=\int { \left( t+\frac { 1 }{ t } \right) } dt\quad =\frac { { t }^{ 2 } }{ 2 } +log|t|+c
=log|tanx|+\frac { 1 }{ 2 } { tan }^{ 2 }x+c

Ex 7.3 Class 12 Maths Question 20.
\frac { cos2x }{ { (cosx+sinx) }^{ 2 } }
Solution:
I=\int { \frac { { cos }^{ 2 }x-{ sin }^{ 2 }x }{ (cosx+sinx)^{ 2 } } dx } =\int { \frac { cosx-sinx }{ cosx+sinx } dx }
put cosx+sinx=t
⇒(-sinx+cox)dx = dt
I=\int { \frac { dt }{ t } } =log|t|+c\quad =log|cosx+sinx|+c

Ex 7.3 Class 12 Maths Question 21.
sin-1 (cos x)
Solution:
\int { { sin }^{ -1 }(cosx)dx } \quad ={ sin }^{ -1 }\left[ sin\left( \frac { \pi }{ 2 } -x \right) \right] dx
\int { \left( \frac { \pi }{ 2 } -x \right) dx } \quad =\frac { \pi x }{ 2 } -\frac { { x }^{ 2 } }{ 2 } +c

Ex 7.3 Class 12 Maths Question 22.
\int { \frac { 1 }{ cos(x-a)cos(x-b) } dx }
Solution:
\frac { 1 }{ sin(a-b) } \int { \frac { sin[(x-b)-(x-a)] }{ cos(x-a)cos(x-b) } dx }
=\frac { 1 }{ sin(a-b) } \left[ \int { tan(x-b)dx-\int { tan(x-a)dx } } \right]
=\frac { 1 }{ sin(a-b) } log\left| \frac { cos(x-a) }{ cos(x-b) } \right| +c

Ex 7.3 Class 12 Maths Question 23.
\int { \frac { { sin }^{ 2 }x-{ cos }^{ 2 }x }{ { sin }^{ 2 }x{ cos }^{ 2 }x } } dx\quad is\quad equal\quad to
(a) tanx+cotx+c
(b) tanx+cosecx+c
(c) -tanx+cotx+c
(d) tanx+secx+c
Solution:
(a) \int { \frac { { sin }^{ 2 }x-{ cos }^{ 2 }x }{ { sin }^{ 2 }x{ cos }^{ 2 }x } } dx
= ∫(sec²x-cosec²x)dx
= tanx+cotx+c

Ex 7.3 Class 12 Maths Question 24.
\int { \frac { e^{ x }(1+x) }{ cos^{ 2 }({ e }^{ x }.{ x }) } } dx\quad is\quad equal\quad to
(a) -cot(e.xx)+c
(b) tan(xex)+c
(c) tan(ex)+c
(d) cot ex+c
Solution:
(b) \int { \frac { e^{ x }(1+x) }{ cos^{ 2 }({ e }^{ x }.{ x }) } } dx
= ∫sec²t dt
= tan t+c = tan(xex)+c

Integrate the functions in exercises 1 to 23

Ex 7.4 Class 12 Maths Question 1.
\frac { { 3x }^{ 2 } }{ { x }^{ 6 }+1 }
Solution:
Let x3 = t ⇒ 3x²dx = dt
\int { \frac { { 3x }^{ 2 } }{ { x }^{ 6 }+1 } dx } =\int { \frac { dt }{ { t }^{ 2 }+1 } } ={ tan }^{ -1 }t+c
= tan-1 (x3)+c

Ex 7.4 Class 12 Maths Question 2.
\frac { 1 }{ \sqrt { 1+{ 4x }^{ 2 } } }
Solution:
\frac { 1 }{ 2 } \int { \frac { dx }{ \sqrt { \frac { 1 }{ 4 } +{ x }^{ 2 } } } } =\frac { 1 }{ 2 } \int { \frac { dx }{ \sqrt { { \left( \frac { 1 }{ 2 } \right) }^{ 2 }+{ x }^{ 2 } } } }
=\frac { 1 }{ 2 } log\left| 2x+\sqrt { 1+{ 4x }^{ 2 } } \right| +c

Ex 7.4 Class 12 Maths Question 3.
\frac { 1 }{ \sqrt { { (2-x) }^{ 2 }+1 } }
Solution:
put (2-x)=t
so that -dx=dt
⇒ dx=-dt
\int { \frac { dx }{ \sqrt { { (2-x) }^{ 2 }+1 } } } =-\int { \frac { dt }{ \sqrt { { t }^{ 2 }+1 } } } =-log|t+\sqrt { { t }^{ 2 }+1 } |+c
=log\left| \frac { 1 }{ (2-x)+\sqrt { { x }^{ 2 }-4x+5 } } \right| +c

Ex 7.4 Class 12 Maths Question 4.
\frac { 1 }{ \sqrt { 9-{ 25x }^{ 2 } } }
Solution:
\int { \frac { dx }{ \sqrt { 9-{ 25x }^{ 2 } } } } =\frac { 1 }{ 5 } \int { \frac { dx }{ \sqrt { { \left( \frac { 3 }{ 5 } \right) }^{ 2 }-{ x }^{ 2 } } } }
=\frac { 1 }{ 5 } { sin }^{ -1 }\left( \frac { x }{ \frac { 3 }{ 5 } } \right) +c\quad =\frac { 1 }{ 5 } { sin }^{ -1 }\left( \frac { 5x }{ 3 } \right) +c

Ex 7.4 Class 12 Maths Question 5.
\frac { 3x }{ 1+{ 2x }^{ 4 } }
Solution:
Put x²=t,so that 2x dx=dt
⇒x dx = \frac { dt }{ 2 }
\therefore \int { \frac { 3x }{ 1+{ 2x }^{ 4 } } dx } =\frac { 1 }{ 2 } \int { \frac { dt }{ 1+{ 2t }^{ 2 } } } =\frac { 3 }{ 4 } \int { \frac { dt }{ { \left( \frac { 1 }{ \sqrt { 2 } } \right) }^{ 2 }+{ t }^{ 2 } } }
=\frac { 3 }{ 2\sqrt { 2 } } { tan }^{ -1 }(\sqrt { 2t } )+c\quad =\frac { 3 }{ 2\sqrt { 2 } } { tan }^{ -1 }(\sqrt { { 2x }^{ 2 } } )+c

Ex 7.4 Class 12 Maths Question 6.
\frac { { x }^{ 2 } }{ 1-{ x }^{ 6 } }
Solution:
put x3 = t,so that 3x²dx = dt
\int { \frac { { x }^{ 2 } }{ 1-{ x }^{ 6 } } dx } \quad =\frac { 1 }{ 3 } \int { \frac { dt }{ 1-{ t }^{ 2 } } \quad =\frac { 1 }{ 6 } log } \left| \frac { 1+t }{ 1-t } \right| +c
=\frac { 1 }{ 6 } log\left| \frac { 1+{ x }^{ 3 } }{ 1-{ x }^{ 3 } } \right| +c

Ex 7.4 Class 12 Maths Question 7.
\frac { x-1 }{ \sqrt { { x }^{ 2 }-1 } }
Solution:
I=\int { \frac { x-1 }{ \sqrt { { x }^{ 2 }-1 } } dx } -\int { \frac { 1 }{ \sqrt { { x }^{ 2 }-1 } } dx } ,I={ I }_{ 1 }-{ I }_{ 2 }
put x²-1 = t,so that 2x dx = dt
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.4 Q7.1

Ex 7.4 Class 12 Maths Question 8.
\frac { { x }^{ 2 } }{ \sqrt { { x }^{ 6 }+{ a }^{ 6 } } }
Solution:
put x3 = t
so that 3x2dx = dt
I=\frac { 1 }{ 3 } \int { \frac { dt }{ { t }^{ 2 }+{ { (a }^{ 3 }) }^{ 2 } } =\frac { 1 }{ 3 } log\left| t+\sqrt { { t }^{ 2 }+{ a }^{ 6 } } \right| +c }
=\frac { 1 }{ 3 } log|{ x }^{ 3 }+\sqrt { { a }^{ 6 }+{ x }^{ 6 } } |+c

Ex 7.4 Class 12 Maths Question 9.
\frac { { sec }^{ 2 }x }{ \sqrt { { tan }^{ 2 }x+4 } }
Solution:
let tanx = t
sec x²dx = dt
I=\int { \frac { dt }{ \sqrt { { t }^{ 2 }+{ (2) }^{ 2 } } } } =log|t+\sqrt { { t }^{ 2 }+4 } |+c
=log|tanx+\sqrt { { tan }^{ 2 }x+4 } |+c

Ex 7.4 Class 12 Maths Question 10.
\frac { 1 }{ \sqrt { { x }^{ 2 }+2x+2 } }
Solution:
\int { \frac { 1 }{ \sqrt { { x }^{ 2 }+2x+2 } } dx } =\int { \frac { dx }{ \sqrt { { (x+1) }^{ 2 }+1 } } }
=log|(x+1)+\sqrt { { x }^{ 2 }+2x+2 } |+c

Ex 7.4 Class 12 Maths Question 11.
\frac { 1 }{ { 9x }^{ 2 }+6x+5 }
Solution:
\int { \frac { 1 }{ { 9x }^{ 2 }+6x+5 } } =\frac { 1 }{ 9 } \int { \frac { dx }{ { \left( x+\frac { 1 }{ 3 } \right) }^{ 2 }{ +\left( \frac { 2 }{ 3 } \right) }^{ 2 } } }
=\frac { 1 }{ 6 } { tan }^{ -1 }\left( \frac { 3x+1 }{ 2 } \right) +c

Ex 7.4 Class 12 Maths Question 12.
\frac { 1 }{ \sqrt { 7-6x-{ x }^{ 2 } } }
Solution:
I=\int { \frac { dx }{ \sqrt { { 4 }^{ 2 }-{ (x+3) }^{ 2 } } } } \quad ={ sin }^{ -1 }\left( \frac { x+3 }{ 4 } \right) +c

Ex 7.4 Class 12 Maths Question 13.
\frac { 1 }{ \sqrt { (x-1)(x-2) } }
Solution:
\int { \frac { 1 }{ \sqrt { (x-1)(x-2) } } dx } =\int { \frac { dx }{ \sqrt { { \left( x-\frac { 3 }{ 2 } \right) }^{ 2 }-{ \left( \frac { 1 }{ 2 } \right) }^{ 2 } } } }
=log\left| x-\frac { 3 }{ 2 } +\sqrt { { x }^{ 2 }-3x+2 } \right| +c

Ex 7.4 Class 12 Maths Question 14.
\frac { 1 }{ \sqrt { 8+3x-{ x }^{ 2 } } }
Solution:
\int { \frac { dx }{ \sqrt { 8+3x-{ x }^{ 2 } } } } =\int { \frac { dx }{ \sqrt { 8-\left( { x }^{ 2 }-3x \right) } } }
=\int { \frac { dx }{ \sqrt { { \left( \frac { \sqrt { 41 } }{ 2 } \right) }^{ 2 }-{ \left( x-\frac { 3 }{ 2 } \right) }^{ 2 } } } } \quad ={ sin }^{ -1 }\left( \frac { 2x-3 }{ \sqrt { 41 } } \right) +c

Ex 7.4 Class 12 Maths Question 15.
\frac { 1 }{ \sqrt { (x-a)(x-b) } }
Solution:
\int { \frac { dx }{ \sqrt { (x-a)(x-b) } } } =\int { \frac { dx }{ { \left( x-\frac { a+b }{ 2 } \right) }^{ 2 }-{ \left( \frac { a-b }{ 2 } \right) }^{ 2 } } }
=log\left| \left( x-\frac { a+b }{ 2 } \right) +\sqrt { (x-a)(x-b) } \right| +c

Ex 7.4 Class 12 Maths Question 16.
\frac { 4x+1 }{ \sqrt { { 2x }^{ 2 }+x-3 } }
Solution:
let\quad I=\int { \frac { 4x+1 }{ \sqrt { { 2x }^{ 2 }+x-3 } } } dx
put 2x²+x-3=t
so that (4x+1)dx=dt
let\quad I=\int { \frac { 4x+1 }{ \sqrt { { 2x }^{ 2 }+x-3 } } } dx
\therefore I=\int { \frac { dt }{ \sqrt { t } } } ={ 2t }^{ \frac { 1 }{ 2 } }+c\quad =2\sqrt { { 2x }^{ 2 }+x-3 } +c

Ex 7.4 Class 12 Maths Question 17.
\frac { x+2 }{ \sqrt { { x }^{ 2 }-1 } }
Solution:
\int { \frac { x+2 }{ \sqrt { { x }^{ 2 }-1 } } dx } \quad =\int { \frac { x }{ \sqrt { { x }^{ 2 }-1 } } dx } +\int { \frac { 2 }{ \sqrt { { x }^{ 2 }-1 } } dx }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.4 Q17.1

Ex 7.4 Class 12 Maths Question 18.
\frac { 5x-2 }{ 1+2x+{ 3x }^{ 2 } }
Solution:
put 5x-2=A\frac { d }{ dx }(1+2x+3x²)+B
⇒ 6A=5, A=\frac { 5 }{ 6 }-2=2A+B, B=-\frac { 11 }{ 3 }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.4 Q18.1

Ex 7.4 Class 12 Maths Question 19.
\frac { 6x+7 }{ \sqrt { (x-5)(x-4) } }
Solution:
\int { \frac { 6x+7 }{ \sqrt { (x-5)(x-4) } } dx } =\int { \frac { (6x+7)dx }{ \sqrt { { x }^{ 2 }-9x+20 } } }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.4 Q19.1

Ex 7.4 Class 12 Maths Question 20.
\frac { x+2 }{ \sqrt { 4x-{ x }^{ 2 } } }
Solution:
I=\int { \frac { x-2 }{ \sqrt { 4-{ (x-2) }^{ 2 } } } dx+4\int { \frac { dx }{ \sqrt { 4-{ (x-2) }^{ 2 } } } } }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.4 Q20.1

Ex 7.4 Class 12 Maths Question 21.
\frac { x+2 }{ \sqrt { { x }^{ 2 }+2x+3 } }
Solution:
I=\frac { 1 }{ 2 } \int { \frac { 2x+2 }{ \sqrt { { x }^{ 2 }+2x+3 } } dx }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.4 Q21.1

Ex 7.4 Class 12 Maths Question 22.
\frac { x+3 }{ { x }^{ 2 }-2x-5 }
Solution:
I=\frac { 1 }{ 2 } \int { \frac { 2x-2 }{ { x }^{ 2 }-2x-5 } dx } +\int { \frac { dx }{ { x }^{ 2 }-2x-5 } }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.4 Q22.1

Ex 7.4 Class 12 Maths Question 23.
\frac { 5x+3 }{ \sqrt { { x }^{ 2 }+4x+10 } }
Solution:
I=\int { \frac { \frac { 5 }{ 2 } (2x+4)+(3-10) }{ \sqrt { { x }^{ 2 }+4x+10 } } dx }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.4 Q23.1

Ex 7.4 Class 12 Maths Question 24.
\int { \frac { dx }{ { x }^{ 2 }+2x+2 } equals }
(a) xtan-1(x+1)+c
(b) (x+1)tan-1x+c
(c) tan-1(x+1)+c
(d) tan-1x+c
Solution:
(b) let\quad I=\int { \frac { dx }{ { x }^{ 2 }+2x+2 } } =\int { \frac { dx }{ (x+1)^{ 2 }+1 } }
= (x+1)tan-1x+c

Ex 7.4 Class 12 Maths Question 25.
\int { \frac { dx }{ \sqrt { 9x-{ 4x }^{ 2 } } } equals }
(a) \frac { 1 }{ 9 } { sin }^{ -1 }\left( \frac { 9x-8 }{ 8 } \right) +c
(b) \frac { 1 }{ 2 } { sin }^{ -1 }\left( \frac { 8x-9 }{ 9 } \right) +c
(c) \frac { 1 }{ 3 } { sin }^{ -1 }\left( \frac { 9x-8 }{ 8 } \right) +c
(d) { sin }^{ -1 }\left( \frac { 9x-8 }{ 9 } \right) +c
Solution:
(b) \int { \frac { dx }{ \sqrt { 9x-{ 4x }^{ 2 } } } } =\frac { 1 }{ 2 } \left[ \frac { dx }{ \sqrt { \left( \frac { 9 }{ 8 } \right) ^{ 2 }-\left[ { x }^{ 2 }-{ \frac { 9 }{ 4 } }x+\left( \frac { 9 }{ 8 } \right) ^{ 2 } \right] } } \right]
\frac { 1 }{ 2 } { sin }^{ -1 }\left( \frac { 8x-9 }{ 9 } \right) +c

Integrate the rational function in exercises 1 to 21

Ex 7.5 Class 12 Maths Question 1.
\frac { x }{ (x+1)(x+2) }
Solution:
let \frac { x }{ (x+1)(x+2) } ≡ \frac { A }{ x+1 } +\frac { B }{ x+2 }
⇒ x ≡ A(x+2)+B(x+1)….(i)
putting x = -1 & x = -2 in (i)
we get A = 1,B = 2
\therefore \int { \frac { 1 }{ (x+1)(x+2) } dx } =\int { \frac { -1 }{ x+1 } dx } +\int { \frac { 2 }{ x+2 } dx }
=-log|x+1| + 2log|x+2|+c

Ex 7.5 Class 12 Maths Question 2.
\frac { 1 }{ { x }^{ 2 }-9 }
Solution:
let \frac { 1 }{ { x }^{ 2 }-9 } =\frac { 1 }{ (x-3)(x+3) } \equiv \frac { A }{ x-3 } +\frac { B }{ x+3 }
⇒ x ≡ A(x+3)+B(x-3)…(i)
put x = 3, -3 in (i)
we get A=\frac { 1 }{ 6 } & B=-\frac { 1 }{ 6 }
\therefore \int { \frac { 1 }{ { x }^{ 2 }-9 } dx } =\frac { 1 }{ 6 } \int { \left[ \frac { 1 }{ x-3 } -\frac { 1 }{ x+3 } \right] dx }
=\frac { 1 }{ 6 } log\left| \frac { x-3 }{ x+3 } \right| +c

Ex 7.5 Class 12 Maths Question 3.
\frac { 3x-1 }{ (x-1)(x-2)(x-3) }
Solution:
Let \frac { 3x-1 }{ (x-1)(x-2)(x-3) } =\frac { A }{ x-1 } +\frac { B }{ x-2 } +\frac { C }{ x-3 }
⇒ 3x-1 = A(x-2)(x-3)+B(x-1)(x-3)+C(x-1)(-2)…..(i)
put x = 1,2,3 in (i)
we get A = 1,B = -5 & C = 4
\therefore I=\int { \frac { 1 }{ x-1 } dx } -5\int { \frac { 1 }{ x-2 } dx } +4\int { \frac { 1 }{ x-3 } dx }
=log|x-1| – 5log|x-2| + 4log|x+3| + C

Ex 7.5 Class 12 Maths Question 4.
\frac { x }{ (x-1)(x-2)(x-3) }
Solution:
let \frac { x }{ (x-1)(x-2)(x-3) } =\frac { A }{ x-1 } +\frac { B }{ x-2 } +\frac { C }{ x-3 }
⇒ x ≡ A(x-2)(x-3)+B(x-1)(x-3)+C(x-1)(x-2)…(i)
put x = 1,2,3 in (i)
A=\frac { 1 }{ 2 } ,B=-2,C=\frac { 3 }{ 2 }
\therefore I=\frac { 1 }{ 2 } \int { \frac { dx }{ x-1 } } -2\int { \frac { dx }{ x-2 } } +\frac { 3 }{ 2 } \int { \frac { dx }{ x-3 } }
=\frac { 1 }{ 2 } log|x-1|-2log|x-2|+\frac { 3 }{ 2 } log|x-3|+c

Ex 7.5 Class 12 Maths Question 5.
\frac { 2x }{ { x }^{ 2 }+3x+2 }
Solution:
let \frac { 2x }{ { x }^{ 2 }+3x+2 } =\frac { 2x }{ (x+1)(x+2) } =\frac { A }{ x+1 } +\frac { B }{ x+2 }
⇒ 2x = A(x+2)+B(x+1)…(i)
put x = -1, -2 in (i)
we get A = -2, B = 4
\therefore \int { \frac { 2x }{ { x }^{ 2 }+3x+2 } dx } =-2\int { \frac { dx }{ x+1 } } +4\int { \frac { dx }{ x+2 } }
=-2log|x+1|+4log|x+2|+c

Ex 7.5 Class 12 Maths Question 6.
\frac { 1-{ x }^{ 2 } }{ x(1-2x) }
Solution:
\frac { 1-{ x }^{ 2 } }{ (x-2{ x }^{ 2 }) }  is an improper fraction therefore we
convert it into a proper fraction. Divide 1 – x² by x – 2x² by long division.
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.5 Q6.1

Ex 7.5 Class 12 Maths Question 7.
\frac { x }{ \left( { x }^{ 2 }+1 \right) \left( x-1 \right) }
Solution:
let \frac { x }{ \left( { x }^{ 2 }+1 \right) \left( x-1 \right) } =\frac { A }{ x-1 } +\frac { Bx+C }{ { x }^{ 2 }+1 }
⇒ x = A(x²+1)+(Bx+C)(x-1)
Put x = 1,0
⇒ A=\frac { 1 }{ 2 } C=\frac { 1 }{ 2 } \Rightarrow B=-\frac { 1 }{ 2 }
\therefore I=\frac { 1 }{ 2 } \int { \frac { dx }{ x-1 } } -\frac { 1 }{ 2 } \int { \frac { x }{ { x }^{ 2 }+1 } dx } +\frac { 1 }{ 2 } \int { \frac { dx }{ { x }^{ 2 }+1 } }
=\frac { 1 }{ 2 } log(x-1)-\frac { 1 }{ 4 } log({ x }^{ 2 }+1)+\frac { 1 }{ 2 } { tan }^{ -1 }x+c

Ex 7.5 Class 12 Maths Question 8.
\frac { x }{ { \left( x-1 \right) }^{ 2 }\left( x+2 \right) }
Solution:
\frac { x }{ { \left( x-1 \right) }^{ 2 }\left( x+2 \right) } =\frac { A }{ x-1 } +\frac { B }{ { \left( x-1 \right) }^{ 2 } } +\frac { C }{ x+2 }
⇒ x ≡ A(x-1)(x+2)+B(x+2)+C(x-1)² …(i)
put x = 1, -2
we get B=\frac { 1 }{ 3 } ,C=\frac { -2 }{ 9 }
\therefore I=\frac { 2 }{ 9 } \int { \frac { 1 }{ x-1 } dx } +\frac { 1 }{ 3 } \int { \frac { 1 }{ { (x-1) }^{ 2 } } dx } -\frac { 2 }{ 9 } \int { \frac { 1 }{ x+2 } dx }
=\frac { 2 }{ 9 } log\left| \frac { x-1 }{ x+2 } \right| -\frac { 1 }{ 3\left( x-1 \right) } +c

Ex 7.5 Class 12 Maths Question 9.
\frac { 3x+5 }{ { x }^{ 3 }-{ x }^{ 2 }-x+1 }
Solution:
let \frac { 3x+5 }{ { x }^{ 2 }(x-1)-1(x-1) }
\frac { 3x+5 }{ (x-1)^{ 2 }(x+1) } =\frac { A }{ x-1 } +\frac { B }{ { (x-1) }^{ 2 } } +\frac { C }{ x+1 }
⇒ 3x+5 = A(x-1)(x+1)+B(x+1)+C(x-1)
put x = 1,-1,0
we get B=4,C=\frac { 1 }{ 2 } ,A=-\frac { 1 }{ 2 }
\therefore I=-\frac { 1 }{ 2 } \int { \frac { dx }{ (x-1) } } +4\frac { dx }{ { (x-1) }^{ 2 } } +\frac { 1 }{ 2 } \int { \frac { dx }{ x+1 } }
=\frac { 1 }{ 2 } log\left| \frac { x+1 }{ x-1 } \right| -\frac { 4 }{ x-1 } +c

Ex 7.5 Class 12 Maths Question 10.
\frac { 2x-3 }{ ({ x }^{ 2 }-1)(2x+3) }
Solution:
\frac { 2x-3 }{ ({ x }^{ 2 }-1)(2x+3) } =\frac { 2x-3 }{ (x-1)(x+1)(2x+3) }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.5 Q10.1

Ex 7.5 Class 12 Maths Question 11.
\frac { 5x }{ (x-1)({ x }^{ 2 }-4) }
Solution:
let \frac { 5x }{ (x-1)({ x }^{ 2 }-4) } =\frac { 5x }{ (x+1)(x+2)(x-2) }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.5 Q11.1

Ex 7.5 Class 12 Maths Question 12.
\frac { { x }^{ 3 }+x+1 }{ { x }^{ 2 }-1 }
Solution:
\frac { { x }^{ 3 }+x+1 }{ { x }^{ 2 }-1 } =x+\frac { 2x+1 }{ (x+1)(x-1) }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.5 Q12.1

Ex 7.5 Class 12 Maths Question 13.
\frac { 2 }{ (1-x)(1+{ x }^{ 2 }) }
Solution:
\frac { 2 }{ (1-x)(1+{ x }^{ 2 }) } =\frac { A }{ 1-x } +\frac { Bx+C }{ 1+{ x }^{ 2 } }
⇒ 2 = A(1+x²) + (Bx+C)(1 -x) …(i)
Putting x = 1 in (i), we get; A = 1
Also 0 = A – B and 2 = A + C ⇒B = A = 1 & C = 1
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.5 Q13.1

Ex 7.5 Class 12 Maths Question 14.
\frac { 3x-1 }{ { (x+2) }^{ 2 } }
Solution:
\frac { 3x-1 }{ { (x+2) }^{ 2 } } \equiv \frac { A }{ x+1 } +\frac { B }{ { (x+2) }^{ 2 } }
=>3x – 1 = A(x + 2) + B …(i)
Comparing coefficients A = -1 and B = -7
\therefore \int { \frac { 3x-1 }{ { (x+2) }^{ 2 } } dx } =3\int { \frac { dx }{ x+2 } } -7\int { \frac { dx }{ { (x+2) }^{ 2 } } }
=3log|x+2|+\frac { 7 }{ x+2 } +c

Ex 7.5 Class 12 Maths Question 15.
\frac { 1 }{ { x }^{ 4 }-1 }
Solution:
\frac { 1 }{ { x }^{ 4 }-1 } =\frac { A }{ x+1 } +\frac { B }{ x-1 } +\frac { Cx+D }{ { x }^{ 2 }+1 }
⇒ 1 ≡ A(x-1)(x²+1) + B(x+1)(x²+1) + (Cx+D)(x+1)(x-1) ….(i)
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.5 Q15.1

Ex 7.5 Class 12 Maths Question 16.
\frac { 1 }{ x({ x }^{ n }+1) }
[Hint : multiply numerator and denominator by xn-1 and put xn = t ]
Solution:
\frac { { x }^{ n-1 } }{ x.{ x }^{ n-1 }({ x }^{ n }+1) } =\frac { { x }^{ n-1 } }{ { x }^{ n }({ x }^{ n }+1) }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.5 Q16.1

Ex 7.5 Class 12 Maths Question 17.
\frac { cosx }{ (1-sinx)(2-sinx) }
Solution:
put sinx = t
so that cosx dx = dt
\therefore I=\int { \frac { 1 }{ (1-t)(2-t) } dt }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.5 Q17.1

Ex 7.5 Class 12 Maths Question 18.
\frac { \left( { x }^{ 2 }+1 \right) \left( { x }^{ 2 }+2 \right) }{ \left( { x }^{ 2 }+3 \right) \left( { x }^{ 2 }+4 \right) }
Solution:
put x²=y
I=1-\frac { 2(2y+5) }{ (y+3)(y+4) }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.5 Q18.1

Ex 7.5 Class 12 Maths Question 19.
\frac { 2x }{ ({ x }^{ 2 }+1)({ x }^{ 2 }+3) }
Solution:
put x²=y
so that 2xdx = dy
\therefore \int { \frac { 2x }{ ({ x }^{ 2 }+1)({ x }^{ 2 }+3) } dx } =\int { \frac { dy }{ (y+1)(y+3) } }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.5 Q19.1

Ex 7.5 Class 12 Maths Question 20.
\frac { 1 }{ x({ x }^{ 4 }-1) }
Solution:
put x4 = t
so that 4x3 dx = dt
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.5 Q20.1

Ex 7.5 Class 12 Maths Question 21.
\frac { 1 }{ { e }^{ x }-1 }
Solution:
Let ex = t ⇒ ex dx = dt
⇒ dx=\frac { dt }{ t }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.5 Q21.1

Ex 7.5 Class 12 Maths Question 22.
choose the correct answer in each of the following :
\int { \frac { xdx }{ (x-1)(x-2) } equals }
(a) log\left| \frac { { (x-1) }^{ 2 } }{ x-2 } \right| +c
(b) log\left| \frac { { (x-2) }^{ 2 } }{ x-1 } \right| +c
(c) log\left| \left( \frac { x-{ 1 }^{ 2 } }{ x-2 } \right) \right| +c
(d) log|(x-1)(x-2)|+c
Solution:
(b) \int { \frac { x }{ (x-1)(x-2) } dx } =\int { \left[ \frac { -1 }{ x-1 } +\frac { 2 }{ x-2 } \right] dx }
log\left| \frac { { (x-2) }^{ 2 } }{ x-1 } \right| +c

Ex 7.5 Class 12 Maths Question 23.
\int { \frac { dx }{ x({ x }^{ 2 }+1) } equals }
(a) log|x|-\frac { 1 }{ 2 } log({ x }^{ 2 }+1)+c
(b) log|x|+\frac { 1 }{ 2 } log({ x }^{ 2 }+1)+c
(c) -log|x|+\frac { 1 }{ 2 } log({ x }^{ 2 }+1)+c
(d) \frac { 1 }{ 2 } log|x|+log({ x }^{ 2 }+1)+c
Solution:
(a) let \frac { 1 }{ x\left( { x }^{ 2 }+1 \right) } =\frac { A }{ x } +\frac { Bx+C }{ { x }^{ 2 }+1 }
⇒ 1 = A(x²+1)+(Bx+C)(x)
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.5 Q23.1

Integrate the functions in Exercises 1 to 22.

Ex 7.6 Class 12 Maths Question 1.
x sinx
Solution:
By part integration
∫x sinx dx = x(-cosx) – ∫1(-cosx)dx
=-x cosx + ∫cosxdx
=-x cosx + sinx + c

Ex 7.6 Class 12 Maths Question 2.
x sin3x
Solution:
∫x sin3x dx = x\left( -\frac { cos3x }{ 3 } \right) -\int { 1 } .\left( \frac { -cos3x }{ 3 } \right) dx
=-\frac { 1 }{ 3 } x\quad cos3x+\frac { 1 }{ 9 } sin3x+c

Ex 7.6 Class 12 Maths Question 3.
{ x }^{ 2 }{ e }^{ x }
Solution:
\int { { x }^{ 2 }{ e }^{ x } } dx={ x }^{ 2 }{ e }^{ x }-2{ x }{ e }^{ x }+2{ e }^{ x }+c
={ e }^{ x }\left( { x }^{ 2 }-2x+2 \right) +c

Ex 7.6 Class 12 Maths Question 4.
x logx
Solution:
\int { xlogx\quad dx } =logx\int { xdx } -\int { \left[ \frac { d }{ dx } (logx)\int { xdx } \right] dx }
=\frac { { x }^{ 2 } }{ 2 } logx-\frac { 1 }{ 2 } \int { x\quad dx } =\frac { { x }^{ 2 } }{ 2 } logx-\frac { 1 }{ 4 } { x }^{ 2 }+c

Ex 7.6 Class 12 Maths Question 5.
x log2x
Solution:
\int { x\quad log2xdx } =(log2x)\frac { { x }^{ 2 } }{ 2 } -\int { \frac { 1 }{ 2x } } .2\left( \frac { { x }^{ 2 } }{ 2 } \right) dx
=\frac { { x }^{ 2 } }{ 2 } log|2x|-\frac { 1 }{ 2 } \int { xdx } =\frac { { x }^{ 2 } }{ 2 } log|2x|-\frac { { x }^{ 2 } }{ 4 } +c

Ex 7.6 Class 12 Maths Question 6.
{ x }^{ 2 }logx
Solution:
\int { { x }^{ 2 }logxdx } =log|x|\left( \frac { { x }^{ 3 } }{ 3 } \right) -\int { \frac { 1 }{ x } } \left( \frac { { x }^{ 3 } }{ 3 } \right) dx
=\frac { { x }^{ 3 } }{ 3 } log|x|-\frac { 1 }{ 3 } \int { { x }^{ 2 }dx } =\frac { { x }^{ 3 } }{ 3 } log|x|-\frac { { x }^{ 3 } }{ 9 } +c

Ex 7.6 Class 12 Maths Question 7.
x\quad { sin }^{ -1 }x
Solution:
I=x\quad { sin }^{ -1 }x.\left( \frac { { x }^{ 2 } }{ 2 } \right) -\int { \frac { 1 }{ \sqrt { 1-{ x }^{ 2 } } } } .\frac { { x }^{ 2 } }{ 2 } dx
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.6 Q7.1

Ex 7.6 Class 12 Maths Question 8.
x\quad { tan }^{ -1 }x
Solution:
I=x\quad { tan}^{ -1 }x.\left( \frac { { x }^{ 2 } }{ 2 } \right) -\int { \frac { 1 }{ \sqrt { 1+{ x }^{ 2 } } } } .\frac { { x }^{ 2 } }{ 2 } dx
=\frac { { x }^{ 2 } }{ 2 } { tan }^{ -1 }x-\frac { 1 }{ 2 } \int { \left( 1-\frac { 1 }{ 1+{ x }^{ 2 } } \right) dx }
=\frac { { x }^{ 2 } }{ 2 } { tan }^{ -1 }x-\frac { 1 }{ 2 } x+\frac { 1 }{ 2 } { tan }^{ -1 }x+c

Ex 7.6 Class 12 Maths Question 9.
x\quad { cos }^{ -1 }x
Solution:
let I = \int { x } { cos }^{ -1 }xdx=\int { { cos }^{ -1 }x } .xdx
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.6 Q9.1

Ex 7.6 Class 12 Maths Question 10.
{ (sin }^{ -1 }{ x })^{ 2 }
Solution:
put\quad { sin }^{ -1 }x=\theta \Rightarrow x=sin\theta \Rightarrow dx=cos\theta d\theta
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.6 Q10.1

Ex 7.6 Class 12 Maths Question 11.
\frac { x\quad { cos }^{ -1 }x }{ \sqrt { 1-{ x }^{ 2 } } }
Solution:
put\quad { cos }^{ -1 }x=t\quad so\quad that\frac { x\quad { cos }^{ -1 }x }{ \sqrt { 1-{ x }^{ 2 } } } dx=dt
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.6 Q11.1

Ex 7.6 Class 12 Maths Question 12.
x sec²x
Solution:
∫x sec²x dx =x(tanx)-∫1.tanx dx
= x tanx+log cosx+c

Ex 7.6 Class 12 Maths Question 13.
{ ta }n^{ -1 }x
Solution:
\int { { tan }^{ -1 }xdx } =x{ tan }^{ -1 }x-\frac { 1 }{ 2 } \int { \frac { 2x }{ 1+{ x }^{ 2 } } dx }
=x{ tan }^{ -1 }x-\frac { 1 }{ 2 } log|1+{ x }^{ 2 }|+c

Ex 7.6 Class 12 Maths Question 14.
x(logx)²
Solution:
∫x(logx)² dx
=\frac { { x }^{ 2 } }{ 2 } { (logx) }^{ 2 }-\left[ (logx)\frac { { x }^{ 2 } }{ 2 } -\int { \frac { 1 }{ x } \frac { { x }^{ 2 } }{ 2 } dx } \right]
=\frac { { x }^{ 2 } }{ 2 } { (logx) }^{ 2 }-\frac { { x }^{ 2 } }{ 2 } logx+\frac { 1 }{ 4 } { x }^{ 2 }+c

Ex 7.6 Class 12 Maths Question 15.
(x²+1)logx
Solution:
∫(x²+1)logx dx
=logx\left( \frac { { x }^{ 3 } }{ 3 } +x \right) -\int { \frac { 1 }{ x } \left( \frac { { x }^{ 3 } }{ 3 } +x \right) dx }
=\left( \frac { { x }^{ 3 } }{ 3 } +x \right) logx-\frac { { x }^{ 3 } }{ 9 } -x+c

Ex 7.6 Class 12 Maths Question 16.
{ e }^{ x }(sinx+cosx)
Solution:
put\quad { e }^{ x }sinx=t\Rightarrow { e }^{ x }(sinx+cosx)dx=dt
\therefore \int { { e }^{ x }(sinx+cosx)dx } =\int { dt } =t+c
={ e }^{ x }sinx+c

Ex 7.6 Class 12 Maths Question 17.
\frac { { xe }^{ x } }{ { (1+x) }^{ 2 } }
Solution:
\int { \frac { { xe }^{ x } }{ { (1+x) }^{ 2 } } }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.6 Q17.1

Ex 7.6 Class 12 Maths Question 18.
\frac { { e }^{ x }(1+sinx) }{ 1+cosx }
Solution:
I=\int { { e }^{ x } } \left[ \frac { 1+2sin\frac { x }{ 2 } cos\frac { x }{ 2 } }{ 2{ cos }^{ 2 }\frac { x }{ 2 } } \right] dx
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.6 Q18.1

Ex 7.6 Class 12 Maths Question 19.
{ e }^{ x }\left( \frac { 1 }{ x } -\frac { 1 }{ { x }^{ 2 } } \right)
Solution:
put \frac { { e }^{ x } }{ x } =t\Rightarrow { e }^{ x }\left( \frac { 1 }{ x } -\frac { 1 }{ { x }^{ 2 } } \right) dx=dt
\therefore I=\int { dt } =t+c=\frac { { e }^{ x } }{ x } +c

Ex 7.6 Class 12 Maths Question 20.
\frac { { (x-2)e }^{ x } }{ { (x-1) }^{ 3 } }
Solution:
I=\int { { e }^{ x }\left[ \frac { 1 }{ { (x-1) }^{ 2 } } -\frac { 2 }{ { (x-1) }^{ 3 } } \right] dx }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.6 Q20.1

Ex 7.6 Class 12 Maths Question 21.
{ e }^{ 2x }sinx
Solution:
let I=\int { { e }^{ 2x }sinx }
={ e }^{ 2x }(-cosx)-\int { 2{ e }^{ 2x }(-cosx)dx }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.6 Q21.1

Ex 7.6 Class 12 Maths Question 22.
{ sin }^{ -1 }\left( \frac { 2x }{ 1+{ x }^{ 2 } } \right)
Solution:
Put x = tan t
so that dx = sec² t dt
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.6 Q22.1

Choose the correct answer in exercise 23 and 24

Ex 7.6 Class 12 Maths Question 23.
\int { { x }^{ 2 }{ e }^{ { x }^{ 3 } } } dx\quad equals
(a) \frac { 1 }{ 3 } { e }^{ { x }^{ 3 } }+c
(b) \frac { 1 }{ 3 } +{ e }^{ { x }^{ 2 } }+c
(c) \frac { 1 }{ 2 } { e }^{ { x }^{ 3 } }+c
(d) \frac { 1 }{ 2 } { e }^{ { x }^{ 2 } }+c
Solution:
(a) let x³ = t
⇒3x² dx = dt
\therefore \int { { x }^{ 2 }{ e }^{ { x }^{ 3 } }dx } =\frac { 1 }{ 3 } \int { { e }^{ t }dt } =\frac { 1 }{ 3 } { e }^{ t }+c=\frac { 1 }{ 3 } { e }^{ { x }^{ 3 } }+c

Ex 7.6 Class 12 Maths Question 24.
\int { { e }^{ x }secx(1+tanx) } dx\quad equals
(a) { e }^{ x }cosx+c
(b) { e }^{ x }secx+c
(c) { e }^{ x }sinx+c
(d) { e }^{ x }tanx+c
Solution:
(b) \int { { e }^{ x }(secx+secx\quad tanx)dx } ={ e }^{ x }secx+c

Integral the function in exercises 1 to 9

Ex 7.7 Class 12 Maths Question 1.
\sqrt { 4-{ x }^{ 2 } }
Solution:
let\quad I=\int { \sqrt { 4-{ x }^{ 2 } } } dx=\int { \sqrt { { (2) }^{ 2 }-{ x }^{ 2 } } dx }
=\frac { x\sqrt { 4-{ x }^{ 2 } } }{ 2 } +2{ sin }^{ -1 }\left( \frac { x }{ 2 } \right) +c

Ex 7.7 Class 12 Maths Question 2.
\sqrt { 1-{ 4x }^{ 2 } }
Solution:
\int { \sqrt { 1-{ 4x }^{ 2 } } } dx=2\int { \sqrt { { \left( \frac { 1 }{ 2 } \right) }^{ 2 }-{ x }^{ 2 } } } dx
=\frac { x\sqrt { 1-{ 4x }^{ 2 } } }{ 2 } +\frac { 1 }{ 4 } { sin }^{ -1 }(2x)+c

Ex 7.7 Class 12 Maths Question 3.
\sqrt { { x }^{ 2 }+4x+6 }
Solution:
\int { \sqrt { { x }^{ 2 }+4x+6 } } dx=\int { \sqrt { { (x+2) }^{ 2 }+{ (\sqrt { 2 } ) }^{ 2 } } } dx
=\frac { x+2 }{ 2 } \sqrt { { x }^{ 2 }+4x+6 } +log\left| (x+2)+\sqrt { { x }^{ 2 }+4x+6 } \right| +c

Ex 7.7 Class 12 Maths Question 4.
\sqrt { { x }^{ 2 }+4x+1 }
Solution:
\int { \sqrt { { x }^{ 2 }+4x+1 } } dx=\int { \sqrt { { (x+2) }^{ 2 }-{ (\sqrt { 3 } ) }^{ 2 } } } dx
=\frac { x+2 }{ 2 } \sqrt { { x }^{ 2 }+4x+1 } -\frac { 3 }{ 2 } log\left| (x+2)+\sqrt { { x }^{ 2 }+4x+1 } \right| +c

Ex 7.7 Class 12 Maths Question 5.
\sqrt { 1-4x-{ x }^{ 2 } }
Solution:
\int { \sqrt { 1-4x-{ x }^{ 2 } } } dx=\int { \sqrt { { (5) }^{ 2 }-{ (x+2) }^{ 2 } } dx }
=\frac { x+2 }{ 2 } \sqrt { 5-{ (x+2) }^{ 2 } } dx

Ex 7.7 Class 12 Maths Question 6.
\sqrt { { x }^{ 2 }+4x-5 }
Solution:
\int { \sqrt { { x }^{ 2 }+4x-5 } } dx=\int { \sqrt { { (x+2) }^{ 2 }-{ (3) }^{ 2 } } } dx
=\frac { x+2 }{ 2 } \sqrt { { x }^{ 2 }+4x-5 } -\frac { 9 }{ 2 } log|x+2+\sqrt { { x }^{ 2 }+4x-5 } |+c

Ex 7.7 Class 12 Maths Question 7.
\sqrt { 1+3x-{ x }^{ 2 } }
Solution:
\int { \sqrt { 1-\left( { x }^{ 2 }-3x \right) } } dx
=\int { \sqrt { { \left( \frac { \sqrt { 13 } }{ 2 } \right) }^{ 2 }-{ \left( x-\frac { 3 }{ 2 } \right) }^{ 2 } } } dx
=\frac { 2x-3 }{ 4 } \sqrt { 1+3x-{ x }^{ 2 } } +\frac { 13 }{ 8 } { sin }^{ -1 }\left[ \frac { 2x-3 }{ \sqrt { 3 } } \right] +c

Ex 7.7 Class 12 Maths Question 8.
\sqrt { { x }^{ 2 }+3x }
Solution:
\int { \sqrt { { x }^{ 2 }+3x } } dx=\int { \sqrt { { \left( x+\frac { 3 }{ 2 } \right) }^{ 2 }-{ \left( \frac { 3 }{ 2 } \right) }^{ 2 } } } dx
=\frac { 2x+3 }{ 4 } \sqrt { { x }^{ 2 }+3x } -\frac { 9 }{ 8 } log\left| x+\frac { 3 }{ 2 } +\sqrt { { x }^{ 2 }+3x } \right| +c

Ex 7.7 Class 12 Maths Question 9.
\sqrt { 1+\frac { { x }^{ 2 } }{ 9 } }
Solution:
\int { \sqrt { 1+\frac { { x }^{ 2 } }{ 9 } } } dx=\frac { 1 }{ 3 } \int { \sqrt { { x }^{ 2 }+{ 3 }^{ 2 } } }
=\frac { 1 }{ 6 } \left[ x\sqrt { { x }^{ 2 }+9 } +9log|x+\sqrt { { x }^{ 2 }+9 } | \right] +c

Choose the correct answer in the Exercises 10 to 11:

Ex 7.7 Class 12 Maths Question 10.
\int { \sqrt { 1+{ x }^{ 2 } } } dx\quad is\quad equal\quad to
(a) \frac { x }{ 2 } \sqrt { 1+{ x }^{ 2 } } +\frac { 1 }{ 2 } log|x+\sqrt { 1+{ x }^{ 2 } } |+c
(b) \frac { 2 }{ 3 } { \left( 1+{ x }^{ 2 } \right) }^{ \frac { 3 }{ 2 } }+c
(c) \frac { 2 }{ 3 } x{ \left( 1+{ x }^{ 2 } \right) }^{ \frac { 3 }{ 2 } }+c
(d) \frac { { x }^{ 2 } }{ 2 } \sqrt { 1+{ x }^{ 2 } } +\frac { 1 }{ 2 } { x }^{ 2 }log\left| x+\sqrt { 1+{ x }^{ 2 } } \right| +c
Solution:
(a) \int { \sqrt { 1+{ x }^{ 2 } } } dx
=\frac { x }{ 2 } \sqrt { 1+{ x }^{ 2 } } +\frac { 1 }{ 2 } log(x+\sqrt { 1+{ x }^{ 2 } } )+c

Ex 7.7 Class 12 Maths Question 11.
\int { \sqrt { { x }^{ 2 }-8x+7 } } dx\quad is\quad equal\quad to
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.7 Q11.1
Solution:
(d) \int { \sqrt { { x }^{ 2 }-8x+7 } } dx=\int { \sqrt { { (x-4) }^{ 2 }-{ (3) }^{ 2 } } } dx
=\frac { x-4 }{ 2 } \sqrt { { x }^{ 2 }-8x+7 } -\frac { 9 }{ 2 } log\left| (x-4)+\sqrt { { x }^{ 2 }+8x+7 } \right| +c

Evaluate the following definite integral as limit of sums.

Ex 7.8 Class 12 Maths Question 1.
\int _{ a }^{ b }{ x\quad dx }
Solution:
on comparing
\int _{ a }^{ b }{ x\quad dx } \quad with\quad \int _{ a }^{ b }{ f(x)dx }
we have
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.8 Q1.1

Ex 7.8 Class 12 Maths Question 2.
\int _{ 0 }^{ 5 }{ (x+1)dx }
Solution:
on comparing
\int _{ 0 }^{ 5 }{ (x+1)dx } \quad with\quad \int _{ 0 }^{ 5 }{ f(x)dx }
we have f(x) = x+1, a = 0, b = 5
and nh = b-a = 5-0 = 5
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.8 Q2.1

Ex 7.8 Class 12 Maths Question 3.
\int _{ 2 }^{ 3 }{ { x }^{ 2 } } dx
Solution:
compare
\int _{ 2 }^{ 3 }{ { x }^{ 2 } } dx\quad with\quad \int _{ a }^{ b }{ f({ x }) } dx
we have
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.8 Q3.1

Ex 7.8 Class 12 Maths Question 4.
\int _{ 1 }^{ 4 }{ ({ x }^{ 2 }-x) } dx
Solution:
compare
\int _{ 1 }^{ 4 }{ ({ x }^{ 2 }-x) } dx\quad with\quad \int _{ a }^{ b }{ f({ x }) } dx
we have f(x) = x²-x and a = 1, b = 4
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.8 Q4.1

Ex 7.8 Class 12 Maths Question 5.
\int _{ -1 }^{ 1 }{ { e }^{ x } } dx\quad
Solution:
compare
\int _{ -1 }^{ 1 }{ { e }^{ x } } dx\quad with\quad \int _{ a }^{ b }{ f({ x }) } dx
we have
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.8 Q5.1

Ex 7.8 Class 12 Maths Question 6.
\int _{ 0 }^{ 4 }{ { (x+e }^{ 2x }) } dx\quad
Solution:
let f(x) = x + e2x,
a = 0, b = 4
and nh = b – a = 4 – 0 = 4

Evaluate the definite integrals in Exercise 1 to 20.

Ex 7.9 Class 12 Maths Question 1.
\int _{ -1 }^{ 1 }{ { (x+1 }) } dx\quad
Solution:
{ =\left[ \frac { { x }^{ 2 } }{ 2 } +x \right] }_{ -1 }^{ 1 }=\frac { 1 }{ 2 } (1-1)+(1+1)\quad =2

Ex 7.9 Class 12 Maths Question 2.
\int _{ 2 }^{ 3 }{ \frac { 1 }{ x } dx }
Solution:
={ \left[ log\quad x \right] }_{ 2 }^{ 3 }\quad =log3-log2\quad =log\frac { 3 }{ 2 }

Ex 7.9 Class 12 Maths Question 3.
\int _{ 1 }^{ 2 }{ \left( { 4x }^{ 3 }-{ 5x }^{ 2 }+6x+9 \right) dx }
Solution:
={ \left[ \frac { { 4x }^{ 4 } }{ 4 } -\frac { { 5x }^{ 3 } }{ 3 } +\frac { { 6x }^{ 2 } }{ 2 } +9x \right] }_{ 1 }^{ 2 }
={ \left[ { x }^{ 4 }-\frac { 5 }{ 3 } { x }^{ 3 }+{ 3x }^{ 2 }+9x \right] }_{ 1 }^{ 2 }\quad =\frac { 64 }{ 3 }

Ex 7.9 Class 12 Maths Question 4.
\int _{ 0 }^{ \frac { \pi }{ 4 } }{ sin2x\quad dx }
Solution:
={ \left[ -\frac { 1 }{ 2 } cos2x \right] }_{ 0 }^{ \frac { \pi }{ 4 } }\quad =\frac { 1 }{ 2 }

Ex 7.9 Class 12 Maths Question 5.
\int _{ 0 }^{ \frac { \pi }{ 2 } }{ cos2x\quad dx }
Solution:
={ \left[ \frac { 1 }{ 2 } sin2x \right] }_{ 0 }^{ \frac { \pi }{ 2 } }\quad =0

Ex 7.9 Class 12 Maths Question 6.
\int _{ 4 }^{ 5 }{ { e }^{ x }dx }
Solution:
={ \left[ { e }^{ x } \right] }_{ 4 }^{ 5 }\quad ={ e }^{ 5 }-{ e }^{ 4 }

Ex 7.9 Class 12 Maths Question 7.
\int _{ 0 }^{ \frac { \pi }{ 4 } }{ tanx\quad dx }
Solution:
={ \left[ log\quad secx \right] }_{ 0 }^{ \frac { \pi }{ 4 } }\quad =\frac { 1 }{ 2 } log2

Ex 7.9 Class 12 Maths Question 8.
\int _{ \frac { \pi }{ 6 } }^{ \frac { \pi }{ 4 } }{ cosec\quad xdx }
Solution:
=log{ \left( cosecx-cotx \right) }_{ \frac { \pi }{ 6 } }^{ \frac { \pi }{ 4 } }
=log(\sqrt { 2 } -1)-log(2-\sqrt { 3 } )\quad =log\left( \frac { \sqrt { 2 } -1 }{ 2-\sqrt { 3 } } \right)

Ex 7.9 Class 12 Maths Question 9.
\int _{ 0 }^{ 1 }{ \frac { dx }{ \sqrt { 1-{ x }^{ 2 } } } }
Solution:
={ sin }^{ -1 }(1)-{ sin }^{ -1 }(0)\quad =\frac { \pi }{ 2 }

Ex 7.9 Class 12 Maths Question 10.
\int _{ 0 }^{ 1 }{ \frac { dx }{ 1+{ x }^{ 2 } } }
Solution:
={ \left[ { tan }^{ -1 }x \right] }_{ 0 }^{ 1 }\quad ={ tan }^{ -1 }(1)-{ ta }n^{ -1 }(0)\quad =\frac { \pi }{ 4 }

Ex 7.9 Class 12 Maths Question 11.
\int _{ 2 }^{ 3 }{ \frac { dx }{ { x }^{ 2 }-1 } }
Solution:
={ \left[ \frac { 1 }{ 2 } log\left( \frac { x-1 }{ x+1 } \right) \right] }_{ 2 }^{ 3 }\quad =\frac { 1 }{ 2 } log\frac { 3 }{ 2 }

Ex 7.9 Class 12 Maths Question 12.
\int _{ 0 }^{ \frac { \pi }{ 2 } }{ { cos }^{ 2 } } xdx
Solution:
=\int _{ 0 }^{ \frac { \pi }{ 2 } }{ { \frac { 1+cos2x }{ 2 } } } dx=\frac { 1 }{ 2 } { \left[ x+\frac { sin2x }{ 2 } \right] }_{ 0 }^{ \frac { \pi }{ 2 } }=\frac { \pi }{ 4 }

Ex 7.9 Class 12 Maths Question 13.
\int _{ 2 }^{ 3 }{ \frac { x }{ { x }^{ 2 }+1 } } dx
Solution:
=\frac { 1 }{ 2 } \int _{ 2 }^{ 3 }{ \frac { 2x }{ { x }^{ 2 }+1 } } dx\quad =\frac { 1 }{ 2 } { \left[ log\left( { x }^{ 2 }+1 \right) \right] }_{ 2 }^{ 3 }\quad =\frac { 1 }{ 2 } log2

Ex 7.9 Class 12 Maths Question 14.
\int _{ 0 }^{ 1 }{ \frac { 2x+3 }{ { 5x }^{ 2 }+1 } dx }
Solution:
=\frac { 1 }{ 5 } \int _{ 0 }^{ 1 }{ \frac { 10x }{ { 5x }^{ 2 }+1 } dx } +\frac { 3 }{ 5 } \int _{ 0 }^{ 1 }{ \frac { dx }{ { { x }^{ 2 }+\left[ \frac { 1 }{ \sqrt { 5 } } \right] }^{ 2 } } }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.9 Q14.1

Ex 7.9 Class 12 Maths Question 15.
\int _{ 0 }^{ 1 }{ { xe }^{ { x }^{ 2 } }dx }
Solution:
let x² = t ⇒ 2xdx = dt
when x = 0, t = 0 & when x = 1,t = 1
\therefore I=\frac { 1 }{ 2 } \int _{ 0 }^{ 1 }{ { e }^{ t }dt } \quad =\frac { 1 }{ 2 } { \left( { e }^{ t } \right) }_{ 0 }^{ 1 }\quad =\frac { 1 }{ 2 } [e-1]

Ex 7.9 Class 12 Maths Question 16.
\int _{ 1 }^{ 2 }{ \frac { { 5x }^{ 2 } }{ { x }^{ 2 }+4x+3 } dx }
Solution:
\int _{ 1 }^{ 2 }{ \left( 5-\frac { 20x+15 }{ { x }^{ 2 }+4x+3 } \right) dx }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.9 Q16.1

Ex 7.9 Class 12 Maths Question 17.
\int _{ 0 }^{ \frac { \pi }{ 4 } }{ \left( { 2sec }^{ 2 }x+{ x }^{ 3 }+2 \right) dx }
Solution:
={ \left[ 2tanx+\frac { { x }^{ 4 } }{ 4 } +2x \right] }_{ 0 }^{ \frac { \pi }{ 4 } }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.9 Q17.1

Ex 7.9 Class 12 Maths Question 18.
\int _{ 0 }^{ \pi }{ \left( { sin }^{ 2 }\frac { x }{ 2 } -{ cos }^{ 2 }\frac { x }{ 2 } \right) } dx
Solution:
=-\int _{ 0 }^{ \pi }{ cosx } dx\quad =-{ \left[ sinx \right] }_{ 0 }^{ \pi }-(0-0)\quad =0

Ex 7.9 Class 12 Maths Question 19.
\int _{ 0 }^{ 2 }{ \frac { 6x+3 }{ { x }^{ 2 }+4 } } dx
Solution:
=\int _{ 0 }^{ 2 }{ \frac { 6x }{ { x }^{ 2 }+4 } } dx+\int _{ 0 }^{ 2 }{ \frac { 3 }{ { x }^{ 2 }+4 } dx }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.9 Q19.1

Ex 7.9 Class 12 Maths Question 20.
\int _{ 0 }^{ 1 }{ \left( { xe }^{ x }+sin\frac { \pi x }{ 4 } \right) dx }
Solution:
=\int _{ 0 }^{ 1 }{ { xe }^{ x }dx } +\int _{ 0 }^{ 1 }{ sin\frac { \pi x }{ 4 } } dx
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.9 Q20.1

Ex 7.9 Class 12 Maths Question 21.
\int _{ 1 }^{ \sqrt { 3 } }{ \frac { dx }{ { 1+x }^{ 2 } } \quad equals }
(a) \frac { \pi }{ 3 }
(b) \frac { 2\pi }{ 3 }
(c) \frac { \pi }{ 6 }
(d) \frac { \pi }{ 12 }
Solution:
(d) \int _{ 1 }^{ \sqrt { 3 } }{ \frac { dx }{ { 1+x }^{ 2 } } } \quad ={ \left[ { tan }^{ -1 }x \right] }_{ 1 }^{ \sqrt { 3 } }\quad =\frac { \pi }{ 3 } -\frac { \pi }{ 4 } \quad =\frac { \pi }{ 12 }

Ex 7.9 Class 12 Maths Question 22.
\int _{ 0 }^{ \frac { 2 }{ 3 } }{ \frac { dx }{ 4+{ 9x }^{ 2 } } equals }
(a) \frac { \pi }{ 6 }
(b) \frac { \pi }{ 12 }
(c) \frac { \pi }{ 24 }
(d) \frac { \pi }{ 4 }
Solution:
(c) \int _{ 0 }^{ \frac { 2 }{ 3 } }{ \frac { dx }{ 4+{ 9x }^{ 2 } } } \quad =\frac { 1 }{ 9 } \int _{ 0 }^{ \frac { 2 }{ 3 } }{ \frac { dx }{ { \left( \frac { 2 }{ 3 } \right) }^{ 2 }+{ x }^{ 2 } } }
=\frac { 1 }{ 6 } { \left[ { tan }^{ -1 }\left( \frac { 3x }{ 2 } \right) \right] }_{ 0 }^{ \frac { 2 }{ 3 } }\quad =\frac { 1 }{ 6 } \times \frac { \pi }{ 4 } \quad =\frac { \pi }{ 24 }

Evaluate the integrals in Exercises 1 to 8 using substitution.

Ex 7.10 Class 12 Maths Question 1.
\int _{ 0 }^{ 1 }{ \frac { x }{ { x }^{ 2 }+1 } } dx=I
Solution:
Let x² + 1 = t
⇒2xdx = dt
when x = 0, t = 1 and when x = 1, t = 2
\therefore I=\frac { 1 }{ 2 } \int _{ 0 }^{ 1 }{ \frac { dt }{ t } } ={ \left[ \frac { 1 }{ 2logt } \right] }_{ 1 }^{ 2 }\quad =\frac { 1 }{ 2 } log2

Ex 7.10 Class 12 Maths Question 2.
\int _{ 0 }^{ \frac { \pi }{ 2 } }{ \sqrt { sin\phi } { cos }^{ 5 }\phi d\phi =I }
Solution:
I=\int _{ 0 }^{ \frac { \pi }{ 2 } }{ \sqrt { sin\phi } { (1-{ sin }^{ 2 }) }^{ 2 }cos\phi d\phi }
put sinφ = t,so that cosφdφ = dt
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.10 Q2.1

Ex 7.10 Class 12 Maths Question 3.
\int _{ 0 }^{ 1 }{ { sin }^{ -1 } } \left( \frac { 2x }{ 1+{ x }^{ 2 } } \right) dx=I
Solution:
let x = tanθ =>dx = sec²θ dθ
when x = 0 => θ = 0
and when x = 1 => \theta \frac { \pi }{ 4 }
\frac { 1 }{ 2 }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.10 Q3.1

Ex 7.10 Class 12 Maths Question 4.
\int _{ 0 }^{ 2 }{ x\sqrt { x+2 } } dx=I(say)(put\quad x+2={ t }^{ 2 })
Solution:
let x+2 = t =>dx = dt
when x = 0,t = 2 and when x = 2, t = 4
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.10 Q4.1

Ex 7.10 Class 12 Maths Question 5.
\int _{ 0 }^{ \frac { \pi }{ 2 } }{ \frac { sinx\quad dx }{ 1+{ cos }^{ 2 }x } =I }
Solution:
put cosx = t
so that -sinx dx = dt
when x = 0, t = 1; when x=\frac { \pi }{ 2 }, t = 0
\therefore I=\int _{ 1 }^{ 0 }{ \frac { -dt }{ 1+{ t }^{ 2 } } =-{ \left[ { tan }^{ -1 }t \right] }_{ 1 }^{ 0 } } =\frac { \pi }{ 4 }

Ex 7.10 Class 12 Maths Question 6.
\int _{ 0 }^{ 2 }{ \frac { dx }{ x+4-{ x }^{ 2 } } =I }
Solution:
\int _{ 0 }^{ 2 }{ \frac { dx }{ x+4-{ x }^{ 2 } } =I }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.10 Q6.1

Ex 7.10 Class 12 Maths Question 7.
\int _{ -1 }^{ 1 }{ \frac { dx }{ { x }^{ 2 }+2x+5 } =I }
Solution:
I=\int _{ -1 }^{ 1 }{ \frac { dx }{ { (x+1) }^{ 2 }+{ 2 }^{ 2 } } } =\frac { 1 }{ 2 } { \left[ { tan }^{ -1 }\frac { x+1 }{ 2 } \right] }_{ -1 }^{ 1 }\quad =\frac { \pi }{ 8 }

Ex 7.10 Class 12 Maths Question 8.
\int _{ 1 }^{ 2 }{ \left[ \frac { 1 }{ x } -\frac { 1 }{ { 2x }^{ 2 } } \right] { e }^{ 2x }dx } =I
Solution:
let 2x = t ⇒ 2dx = dt
when x = 1, t = 2 and when x = 2, t = 4
I=\int _{ 2 }^{ 4 }{ e } ^{ t }\left( \frac { 1 }{ t } -\frac { 1 }{ { t }^{ 2 } } \right) dt\quad ={ e }^{ t }{ \left[ \frac { 1 }{ t } \right] }_{ 2 }^{ 4 }\quad =\frac { e^{ 2 } }{ 2 } \left[ \frac { { e }^{ 2 } }{ 2 } -1 \right]

Choose the correct answer in Exercises 9 and 10

Ex 7.10 Class 12 Maths Question 9.
The value of integral \int _{ \frac { 1 }{ 3 } }^{ 1 }{ \frac { { { (x-x }^{ 3 }) }^{ \frac { 1 }{ 3 } } }{ { x }^{ 4 } } dx }  is
(a) 6
(b) 0
(c) 3
(d) 4
Solution:
(a) let I = \int _{ \frac { 1 }{ 3 } }^{ 1 }{ \frac { { { (x-x }^{ 3 }) }^{ \frac { 1 }{ 3 } } }{ { x }^{ 4 } } dx } \quad =\int _{ \frac { 1 }{ 3 } }^{ 1 }{ \frac { { x }^{ \frac { 1 }{ 3 } }(1-{ x }^{ 2 })^{ \frac { 1 }{ 3 } } }{ { x }^{ 4 } } dx }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.10 Q9.1

Ex 7.10 Class 12 Maths Question 10.
If\quad f(x)=\int _{ 0 }^{ x }{ tsint,\quad then\quad { f }^{ \prime }(x)\quad is }
(a) cosx+xsinx
(b) xsinx
(c) xcosx
(d) sinx+xcosx
Solution:
(b) f(x)=\int _{ 0 }^{ x }{ tsint\quad dt }
=t(-cost)-\int { 1{ \left[ (-cost)dt \right] }_{ 0 }^{ x } }
=-x cox+sinx

By using the properties of definite integrals, evaluate the integrals in Exercises 1 to 19.

Ex 7.11 Class 12 Maths Question 1.
\int _{ 0 }^{ \frac { \pi }{ 2 } }{ { cos }^{ 2 }x\quad dx } =I
Solution:
I=\frac { 1 }{ 2 } \int _{ 0 }^{ \frac { \pi }{ 2 } }{ (1+cos2x)dx } =\frac { 1 }{ 2 } { \left[ x+\frac { sin2x }{ 2 } \right] }_{ 0 }^{ \frac { \pi }{ 2 } }\quad =\frac { \pi }{ 4 }

Ex 7.11 Class 12 Maths Question 2.
\int _{ 0 }^{ \frac { \pi }{ 2 } }{ \frac { \sqrt { sinx } }{ \sqrt { sinx } +\sqrt { cosx } } dx }
Solution:
let I = \int _{ 0 }^{ \frac { \pi }{ 2 } }{ \frac { \sqrt { sinx } }{ \sqrt { sinx } +\sqrt { cosx } } dx }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.11 Q2.1

Ex 7.11 Class 12 Maths Question 3.
\int _{ 0 }^{ \frac { \pi }{ 2 } }{ \frac { { sin }^{ \frac { 3 }{ 2 } }xdx }{ { sin }^{ \frac { 3 }{ 2 } }x+{ cos }^{ \frac { 3 }{ 2 } }dx } dx }
Solution:
let I = \int _{ 0 }^{ \frac { \pi }{ 2 } }{ \frac { { sin }^{ \frac { 3 }{ 2 } }xdx }{ { sin }^{ \frac { 3 }{ 2 } }x+{ cos }^{ \frac { 3 }{ 2 } }dx } dx }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.11 Q3.1

Ex 7.11 Class 12 Maths Question 4.
\int _{ 0 }^{ \frac { \pi }{ 2 } }{ \frac { { cos }^{ 5 }xdx }{ { sin }^{ 5 }x+{ cos }^{ 5 }x } }
Solution:
let I = \int _{ 0 }^{ \frac { \pi }{ 2 } }{ \frac { { cos }^{ 5 }xdx }{ { sin }^{ 5 }x+{ cos }^{ 5 }x } }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.11 Q4.1

Ex 7.11 Class 12 Maths Question 5.
\int _{ -5 }^{ 5 }{ \left| x+2 \right| dx=I }
Solution:
I=\int _{ -5 }^{ 5 }{ \left| x+2 \right| dx+\int _{ -2 }^{ 5 }{ \left| x+2 \right| dx } }
at x = – 5, x + 2 < 0; at x = – 2, x + 2 = 0; at x = 5, x + 2>0;x + 2<0, x + 2 = 0, x + 2>0
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.11 Q5.1

Ex 7.11 Class 12 Maths Question 6.
\int _{ 2 }^{ 8 }{ |x-5|dx } =I
Solution:
\int _{ 2 }^{ 8 }{ |x-5|dx } =I
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.11 Q6.1

Ex 7.11 Class 12 Maths Question 7.
\int _{ 0 }^{ 1 }{ x(1-x)^{ n }dx } =I
Solution:
\int _{ 0 }^{ 1 }{ x(1-x)^{ n }dx } =I
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.11 Q7.1

Ex 7.11 Class 12 Maths Question 8.
\int _{ 0 }^{ \frac { \pi }{ 4 } }{ log(1+tanx)dx }
Solution:
let I = \int _{ 0 }^{ \frac { \pi }{ 4 } }{ log(1+tanx)dx }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.11 Q8.1

Ex 7.11 Class 12 Maths Question 9.
\int _{ 0 }^{ 2 }{ x\sqrt { 2-x } dx=I }
Solution:
let 2-x = t
⇒ – dx = dt
when x = 0, t = 2 and when x = 2,t = 0
\frac { 1 }{ 2 }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.11 Q9.1

Ex 7.11 Class 12 Maths Question 10.
\int _{ 0 }^{ \frac { \pi }{ 2 } }{ \left( 2logsinx-logsin2x \right) dx=I }
Solution:
\int _{ 0 }^{ \frac { \pi }{ 2 } }{ \left( 2logsinx-logsin2x \right) dx=I }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.11 Q10.1

Ex 7.11 Class 12 Maths Question 11.
\int _{ \frac { -\pi }{ 2 } }^{ \frac { \pi }{ 2 } }{ { sin }^{ 2 } } xdx
Solution:
Let f(x) = sin² x
f(-x) = sin² x = f(x)
∴ f(x) is an even function
\therefore \int _{ \frac { -\pi }{ 2 } }^{ \frac { \pi }{ 2 } }{ { sin }^{ 2 } } xdx\quad =2\int _{ 0 }^{ \frac { \pi }{ 2 } }{ \left[ \frac { 1-cos2x }{ 2 } \right] dx }
={ \left[ x-\frac { sin2x }{ x } \right] }_{ 0 }^{ \frac { \pi }{ 2 } }\therefore I=\frac { \pi }{ 2 }

Ex 7.11 Class 12 Maths Question 12.
\int _{ 0 }^{ \pi }{ \frac { xdx }{ 1+sinx } }
Solution:
let I = \int _{ 0 }^{ \pi }{ \frac { xdx }{ 1+sinx } }  …(i)
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.11 Q12.1

Ex 7.11 Class 12 Maths Question 13.
\int _{ \frac { -\pi }{ 2 } }^{ \frac { \pi }{ 2 } }{ { sin }^{ 7 } } xdx
Solution:
Let f(x) = sin7 xdx
⇒ f(-x) = -sin7 x = -f(x)
⇒ f(x) is an odd function of x
⇒ \int _{ \frac { -\pi }{ 2 } }^{ \frac { \pi }{ 2 } }{ { sin }^{ 7 } } xdx=0

Ex 7.11 Class 12 Maths Question 14.
\int _{ 0 }^{ 2\pi }{ { cos }^{ 5 } } xdx
Solution:
let f(x) = cos5 x
⇒ f(2π – x) = cos5 x
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.11 Q14.1

Ex 7.11 Class 12 Maths Question 15.
\int _{ 0 }^{ \frac { \pi }{ 2 } }{ \frac { sinx-cosx }{ 1+sinx\quad cosx } dx }
Solution:
let I = \int _{ 0 }^{ \frac { \pi }{ 2 } }{ \frac { sinx-cosx }{ 1+sinx\quad cosx } dx }  …(i)
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.11 Q15.1

Ex 7.11 Class 12 Maths Question 16.
\int _{ 0 }^{ \pi }{ log(1+cosx)dx }
Solution:
let I = \int _{ 0 }^{ \pi }{ log(1+cosx)dx }
then I = \int _{ 0 }^{ \pi }{ log[1+cos(\pi -x)]dx }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.11 Q16.1
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.11 Q16.2

Ex 7.11 Class 12 Maths Question 17.
\int _{ 0 }^{ a }{ \frac { \sqrt { x } }{ \sqrt { x } +\sqrt { a-x } } dx }
Solution:
let I = \int _{ 0 }^{ a }{ \frac { \sqrt { x } }{ \sqrt { x } +\sqrt { a-x } } dx }  …(i)
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.11 Q17.1

Ex 7.11 Class 12 Maths Question 18.
\int _{ 0 }^{ 4 }{ \left| x-1 \right| dx=I }
Solution:
I=-\int _{ 0 }^{ 1 }{ (x-1)dx } +\int _{ 1 }^{ 4 }{ (x-1)dx }
=-{ \left[ \frac { { x }^{ 2 } }{ 2 } -x \right] }_{ 0 }^{ 1 }+{ \left[ \frac { { x }^{ 2 } }{ 2 } -x \right] }_{ 1 }^{ 4 }=5

Ex 7.11 Class 12 Maths Question 19.
show that 4\int _{ 0 }^{ a }{ f(x)g(x)dx } =2\int _{ 0 }^{ a }{ f(x)dx }  if f and g are defined as f(x)=f(a-x) and g(x)+g(a-x)=4
Solution:
let I = \int _{ 0 }^{ a }{ f(x)g(x)dx }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.11 Q19.1

Ex 7.11 Class 12 Maths Question 20.
The value of \int _{ \frac { -\pi }{ 2 } }^{ \frac { \pi }{ 2 } }{ \left( { x }^{ 3 }+xcosx+{ tan }^{ 5 }x+1 \right) dx }  is
(a) 0
(b) 2
(c) π
(d) 1
Solution:
(c) let I = \int _{ \frac { -\pi }{ 2 } }^{ \frac { \pi }{ 2 } }{ \left( { x }^{ 3 }+xcosx+{ tan }^{ 5 }x+1 \right) dx }  is
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.11 Q20.1

Ex 7.11 Class 12 Maths Question 21.
The value of \int _{ 0 }^{ \frac { \pi }{ 2 } }{ log\left[ \frac { 4+3sinx }{ 4+3sinx } \right] dx }  is
(a) 2
(b) \frac { 3 }{ 4 }
(c) 0
(d) -2
Solution:
let I = \int _{ 0 }^{ \frac { \pi }{ 2 } }{ log\left[ \frac { 4+3sinx }{ 4+3sinx } \right] dx }
NCERT Solutions for Class 12 Maths Chapter 7 Integrals Ex 7.11 Q21.1

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Class 12th Chapter -6 Application of Derivatives | NCERT Maths Solution | NCERT Solution | Edugrown

It is important that you have a strong foundation in Maths Solutions. This can help you immensely in exams. Because there is no paper pattern set for the board exams. Every year there are different twists and turns in questions asked in board exams. While preparing for maths it becomes to go through every bit of detail. Thus, NCERT Solutions Class 12 Maths can help you lay a strong foundation. There solutions of each and every question given in the NCERT 12 Textbook in this article. There are crucial chapters like integration, algebra, and calculus which you can solve easily using these Class 12 Maths solutions. Using these NCERT Maths Class 12 Solutions can give you an edge over the other students.

NCERT Solutions for Class 12 Maths Chapter : 6 Application of Derivatives

Ex 6.1 Class 12 Maths Question 1.
Find the rate of change of the area of a circle with respect to its radius r when (a) r = 3 cm (b) r = 4 cm
Solution:
Let A be the area of the circle
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.1 Q1.1

Ex 6.1 Class 12 Maths Question 2.
The volume of a cube is increasing at the rate of 8 cm³/s. How fast is the surface area increasing when the length of an edge is 12 cm?
Solution:
Let x be the length of the cube volume V = x³,
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.1 Q2.1

Ex 6.1 Class 12 Maths Question 3.
The radius of a circle is increasing uniformly at the rate of 3 cm/s. Find the rate at which the area of the circle is increasing when the radius is 10 cm.
Solution:
Let r be the radius of the circle.
Area of circle = πr² = A also \frac { dr }{ dt } = 3 cm/ sec.
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.1 Q3.1

Ex 6.1 Class 12 Maths Question 4.
An edge of a variable cube is increasing at the rate of 3 cm/s. How fast is the volume of the cube increasing when the edge is 10 cm long?
Solution:
Let the edge of the cube = x cm
∴ \frac { dx }{ dt } = 3
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.1 Q4.1

Ex 6.1 Class 12 Maths Question 5.
A stone is dropped into a quiet lake and waves move in circles at the speed of 5 cm/s. At the instant when the radius of the circular wave is 8 cm, how fast is the enclosed area increasing?
Solution:
Let r be the radius of a wave circle: \frac { dx }{ dt } = 5cm/sec.
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.1 Q5.1

Ex 6.1 Class 12 Maths Question 6.
The radius of a circle is increasing at the rate of 0.7 cm/s. What is the rate of increase of its circumference?
Solution:
The rate of change of circle w.r.t time t is given
to be 0.7 cm/sec. i.e. \frac { dr }{ dt } = 0.7 cm/sec.
Now, circumference of the circle is c = 2πr
\therefore \frac { dc }{ dt } =\left[ \frac { d }{ dr } \left( 2\pi r \right) .\frac { dr }{ dt } \right] =2\pi \frac { dr }{ dt } =1.4\pi cm/sec

Ex 6.1 Class 12 Maths Question 7.
The length x of a rectangle is decreasing at the rate of 5 cm/minute and the width y is increasing at the rate of 4 cm/minute. When x = 8 cm and y = 6 cm, find the rates of change of
(a) the perimeter, and
(b) the area of the rectangle.
Solution:
(a) The length x of a rectangle is decreasing at dx the rate of 5cm/min. => \frac { dx }{ dt } = – 5cm min …(i)
The width y is increasing at the rate of 4cm/min.
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.1 Q7.1

Ex 6.1 Class 12 Maths Question 8.
A balloon, which always remains spherical on inflation, is being inflated by pumping in 900 cubic centimetres of gas per second. Find the rate at which the radius of the balloon increases when the radius is 15 cm.
Solution:
Volume of the spherical balloon = V = \frac { 4 }{ 3 } \pi { r }^{ 3 }
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.1 Q8.1

Ex 6.1 Class 12 Maths Question 9.
A balloon, which always remains spherical has a variable radius. Find the rate at which its volume is increasing with the radius when the later is 10 cm.
Solution:
Let r be the variable radius of the balloon which is in the form of sphere Vol. of the sphere
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.1 Q9.1

Ex 6.1 Class 12 Maths Question 10.
A ladder 5 m long is leaning against a wall. The bottom of the ladder is pulled along the ground, away from the wall, at the rate of 2cm/s. How fast is its height on the wall decreasing when the foot of the ladder is 4m away from die wall ?
Solution:
Let AB be the ladder and OB be the wall. At an instant,
let OA = x, OB = y,
x² + y² = 25 …(i)
On differentiating,
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.1 Q10.1

Ex 6.1 Class 12 Maths Question 11.
A particle moves along the curve 6y = x3 + 2. Find the points on the curve at which the y-coordinate is changing 8 times as fast as the x-coordinate.
Solution:
We have
6y = x3 + 2…(i)
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.1 Q11.1

Ex 6.1 Class 12 Maths Question 12.
The radius of an air bubble is increasing at the rate of \frac { 1 }{ 2 } cm/s. At what rate is the volume of the bubble increasing when the radius is 1 cm?
Solution:
Let r be the radius then V = \frac { 4 }{ 3 } \pi { r }^{ 3 }
\frac { dr }{ dt } =\frac { 1 }{ 2 } cm/sec
\frac { dv }{ dt } =\frac { d }{ dt } \left( \frac { 4 }{ 3 } \pi { r }^{ 3 } \right) =\frac { 4 }{ 3 } { \pi .3r }^{ 2 }.\frac { dr }{ dt } ={ 2\pi r }^{ 2 }
Hence, the rate of increase of volume when radius is 1 cm = 2π x 1² = 2π cm3/sec.

Ex 6.1 Class 12 Maths Question 13.
A balloon, which always remains spherical, has a variable diameter \frac { 3 }{ 2 }(2x+1) . Find the rate of change of its volume with respect to x.
Solution:
Dia of sphere = \frac { 3 }{ 2 }(2x+1)
∴ Radius = \frac { 3 }{ 4 }(2x+1)
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.1 Q13.1

Ex 6.1 Class 12 Maths Question 14.
Sand is pouring from a pipe at the rate of 12 cm3/s. The falling sand forms a cone on the ground in such a way that the height of the cone is always one-sixth of the radius of the base. How fast is the height of the sand cone increasing when the height is 4 cm?
Solution:
Let r and h be the radius and height of the sand
– cone at time t respectively, h = \frac { r }{ 6 }  …(i)
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.1 Q14.1

Ex 6.1 Class 12 Maths Question 15.
The total cost C (x) in Rupees associated with the production of x units of an item is given by C (x) = 0.007 x3 – 0.003 x2 + 15x + 4000. Find the marginal cost when 17 units are produced.
Solution:
Marginal cost MC = Instantaneous rate of change
of total cost at any level of out put = \frac { dC }{ dx }
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.1 Q15.1

Ex 6.1 Class 12 Maths Question 16.
The total revenue in Rupees received from the sale of x units of a product is given by
R (x) = 13x² + 26x +15. Find the marginal revenue when x = 7.
Solution:
Marginal Revenue (MR)
= Rate of change of total revenue w.r.t. the
number of items sold at an instant = \frac { dR }{ dx }
We know R(x) = 13x² + 26x + 15,
MR = \frac { dR }{ dx }  = 26x + 26 = 26(x+1)
Now x = 7, MR = 26 (x + 1) = 26 (7 + 1) = 208
Hence, Marginal Revenue = Rs 208.

Choose the correct answer in the Exercises 17 and 18.

Ex 6.1 Class 12 Maths Question 17.
The rate of change of the area of a circle with respect to its radius r at r = 6 cm is
(a) 10π
(b) 12π
(c) 8π
(d) 11π
Solution:
(b) ∵ A = πr² => \frac { dA }{ dr }  = 2π x 6 = 12π cm²/radius

Ex 6.1 Class 12 Maths Question 18.
The total revenue in Rupees received from the sale of x units of a product is given by R (x) = 3x² + 36x + 5. The marginal revenue, when x = 15 is
(a) 116
(b) 96
(c) 90
(d) 126
Solution:
(d) R(x) = 3x² + 36x + 5 ,
MR = \frac { dR }{ dx }  = 6x + 36 ,
At x = 15; \frac { dR }{ dx }  = 6 x 15 + 36 = 90 + 36 = 126

Ex 6.2 Class 12 Maths Question 1.
Show that the function given by f (x) = 3x+17 is strictly increasing on R.
Solution:
f(x) = 3x + 17
∴ f’ (x) = 3>0 ∀ x∈R
⇒ f is strictly increasing on R.

Ex 6.2 Class 12 Maths Question 2.
Show that the function given by f (x) = e2x is strictly increasing on R.
Solution:
We have f (x) = e2x
⇒ f’ (x) = 2e2x
Case I When x > 0, then f’ (x) = 2e2x
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.2 Q2.1

Ex 6.2 Class 12 Maths Question 3.
Show that the function given by f (x) = sin x is
(a) strictly increasing in \left( 0,\frac { \pi }{ 2 } \right)
(b) strictly decreasing in \left( \frac { \pi }{ 2 } ,\pi \right)
(c) neither increasing nor decreasing in (0, π)
Solution:
We have f(x) = sinx
∴ f’ (x) = cosx
(a) f’ (x) = cos x is + ve in the interval \left( 0,\frac { \pi }{ 2 } \right)
⇒ f(x) is strictly increasing on \left( 0,\frac { \pi }{ 2 } \right)
(b) f’ (x) = cos x is a -ve in the interval \left( \frac { \pi }{ 2 } ,\pi \right)
⇒ f (x) is strictly decreasing in \left( \frac { \pi }{ 2 } ,\pi \right)
(c) f’ (x) = cos x is +ve in the interval \left( 0,\frac { \pi }{ 2 } \right)
while f’ (x) is -ve in the interval \left( \frac { \pi }{ 2 } ,\pi \right)
∴ f(x) is neither increasing nor decreasing in (0,π)

Ex 6.2 Class 12 Maths Question 4.
Find the intervals in which the function f given by f(x) = 2x² – 3x is
(a) strictly increasing
(b) strictly decreasing
Solution:
f(x) = 2x² – 3x
⇒ f’ (x) = 4x – 3
⇒ f’ (x) = 0 at x = \frac { 3 }{ 4 }
The point x=\frac { 3 }{ 4 } divides the real
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.2 Q4.1

Ex 6.2 Class 12 Maths Question 5.
Find the intervals in which the function f given by f (x) = 2x3 – 3x² – 36x + 7 is
(a) strictly increasing
(b) strictly decreasing
Solution:
f(x) = 2x3 – 3x² – 36x + 7;
f (x) = 6 (x – 3) (x + 2)
⇒ f’ (x) = 0 at x = 3 and x = – 2
The points x = 3, x = – 2, divide the real line into three disjoint intervals viz. (-∞,-2), (-2,3), (3,∞)
Now f’ (x) is +ve in the intervals (-∞, -2) and (3,∞). Since in the interval (-∞, -2) each factor x – 3, x + 2 is -ve.
⇒ f’ (x) = + ve.
(a) f is strictly increasing in (-∞, -2)∪(3,∞)
(b) In the interval (-2,3), x+2 is +ve and x-3 is -ve.
f (x) = 6(x – 3)(x + 2) = + x – = -ve
∴ f is strictly decreasing in the interval (-2,3).

Ex 6.2 Class 12 Maths Question 6.
Find the intervals in which the following functions are strictly increasing or decreasing:
(a) x² + 2x – 5
(b) 10 – 6x – 2x²
(c) – 2x3 – 9x² – 12x + 1
(d) 6 – 9x – x²
(e) (x + 1)3(x – 3)3
Solution:
(c) Let f(x) = – 2x3 – 9x2 – 12x + 1
∴ f’ (x) = – 6x2 – 18x – 12
= – 6(x2 + 3x + 2)
f'(x) = – 6(x + 1)(x + 2), f’ (x) = 0 gives x = -1 or x = -2
The points x = – 2 and x = – 1 divide the real line into three disjoint intervals namely ( – ∞, – 2) ( – 2, – 1) and( – 1 ∞).
In the interval (-∞,-2) i.e.,-∞<x<-2 (x+ 1) (x+2) are -ve.
∴f’ (x) = (-) (-) (- ) = – ve.
⇒ f (x) is decreasing in (-∞,-2)
In the interval (-2, -1) i.e., – 2 < x < -1,
(x + 1) is -ve and (x + 2) is + ve.
∴ f'(x) = (-)(-) (+) = + ve.
⇒ f (x) is increasing in (-2, -1)
In the interval (-1,∞) i.e.,-1 <x<∞,(x + 1) and (x + 2) are both positive. f’ (x) = (-) (+) (+) = -ve.
⇒ f (x) is decreasing in (-1, ∞)
Hence, f (x) is increasing for – 2 < x < – 1 and decreasing for x<-2 and x>-1.

Ex 6.2 Class 12 Maths Question 7.
Show that y=log(1+x)-\frac { 2x }{ 2+x } x>-1, is an increasing function of x throughout its domain.
Solution:
let f(x)=log(1+x)-\frac { 2x }{ 2+x } x>-1
f’ (x) = \frac { { x }^{ 2 } }{ { (x+1)(x+2) }^{ 2 } }
For f (x) to be increasing f’ (x) > 0
\Rightarrow \frac { 1 }{ x+1 } >0\Rightarrow x>-1
Hence, y=log(1+x)-\frac { 2x }{ 2+x }  is an increasing function of x for all values of x > – 1.

Ex 6.2 Class 12 Maths Question 8.
Find the values of x for which y = [x (x – 2)]² is an increasing function.
Solution:
y = x4 – 4x3 + 4x2
∴ \frac { dy }{ dx } = 4x3 – 12x2 + 8x
For the function to be increasing \frac { dy }{ dx } >0
4x3 – 12x2 + 8x>0
⇒ 4x(x – 1)(x – 2)>0
For 0 < x < 1, \frac { dy }{ dx } = (+)(-)(-) = +ve and for x > 2, \frac { dy }{ dx } = (+) (+) (+) = +ve
Thus, the function is increasing for 0 < x < 1 and x > 2.

Ex 6.2 Class 12 Maths Question 9.
Prove that y=\frac { 4sin\theta }{ (2+cos\theta ) } -\theta  is an increasing function of θ in \left[ 0,\frac { \pi }{ 2 } \right]
Solution:
\frac { dy }{ dx } =\frac { 8cos\theta +4 }{ { (2+cos\theta ) }^{ 2 } } -1=\frac { cos\theta (4-cos\theta ) }{ { (2+cos\theta ) }^{ 2 } }
For the function to be increasing \frac { dy }{ dx } > 0
⇒ cosθ(4-cos2θ)>0
⇒ cosθ>0
⇒ θ∈\left[ 0,\frac { \pi }{ 2 } \right]1

Ex 6.2 Class 12 Maths Question 10.
Prove that the logarithmic function is strictly increasing on (0, ∞).
Solution:
Let f (x) = log x
Now, f’ (x) = \frac { 1 }{ x } ; When takes the
values x > 0, \frac { 1 }{ x } > 0, when x > 0,
∵ f’ (x) > 0
Hence, f (x) is an increasing function for x > 0 i.e

Ex 6.2 Class 12 Maths Question 11.
Prove that the function f given by f (x) = x² – x + 1 is neither strictly increasing nor strictly decreasing on (-1,1).
Solution:
Given
f (x) = x² – x + 1
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.2 Q11.1
∴ f (x) is neither increasing nor decreasing on (-1,1).

Ex 6.2 Class 12 Maths Question 12.
Which of the following functions are strictly decreasing on \left[ 0,\frac { \pi }{ 2 } \right]
(a) cos x
(b) cos 2x
(c) cos 3x
(d) tan x
Solution:
(a) We have f (x) = cos x
∴ f’ (x) = – sin x < 0 in \left[ 0,\frac { \pi }{ 2 } \right]
∴ f’ (x) is a decreasing function.
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.2 Q12.1

Ex 6.2 Class 12 Maths Question 13.
On which of the following intervals is the function f given by f (x )= x100 + sin x – 1 strictly decreasing ?
(a) (0,1)
(b) \left[ \frac { \pi }{ 2 } ,\pi \right]
(c) \left[ 0,\frac { \pi }{ 2 } \right]
(d) none of these
Solution:
(d) f(x) = x100 + sin x – 1
∴ f’ (x)= 100x99+ cos x
(a) for(-1, 1)i.e.,- 1 <x< 1,-1 <x99< 1
⇒ -100<100x99<100;
Also 0 ⇒ f’ (x) can either be +ve or -ve on(-1, 1)
∴ f (x) is neither increasing nor decreasing on (-1,1).
(b) for (0,1) i.e. 0<x< 1 x99 and cos x are both +ve ∴ f’ (x) > 0
⇒ f (x) is increasing on(0,1)
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.2 Q13.1

Ex 6.2 Class 12 Maths Question 14.
Find the least value of a such that the function f given by f (x) = x² + ax + 1 is strictly increasing on (1,2).
Solution:
We have f (x) = x² + ax + 1
∴ f’ (x) = 2x + a.
Since f (x) is an increasing function on (1,2)
f’ (x) > 0 for all 1 < x < 2 Now, f” (x) = 2 for all x ∈ (1,2) ⇒ f” (x) > 0 for all x ∈ (1,2)
⇒ f’ (x) is an increasing function on (1,2)
⇒ f’ (x) is the least value of f’ (x) on (1,2)
But f’ (x)>0 ∀ x∈ (1,2)
∴ f’ (1)>0 =>2 + a>0
⇒ a > – 2 : Thus, the least value of a is – 2.

Ex 6.2 Class 12 Maths Question 15.
Let I be any interval disjoint from (-1,1). Prove that the function f given by f(x)=x+\frac { 1 }{ x }  is strictly increasing on I.
Solution:
Given
f(x)=x+\frac { 1 }{ x }
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.2 Q15.1
Hence, f’ (x) is strictly increasing on I.

Ex 6.2 Class 12 Maths Question 16.
Prove that the function f given by f (x) = log sin x is strictly increasing on \left( 0,\frac { \pi }{ 2 } \right)  and strictly decreasing on
\left( \frac { \pi }{ 2 } ,\pi \right)
Solution:
f’ (x) = \frac { 1 }{ sin\quad x } .cos\quad x\quad cot\quad x\quad
when 0 < x < \frac { \pi }{ 2 } , f’ (x) is +ve; i.e., increasing
When \frac { \pi }{ 2 }  < x < π, f’ (x) is – ve; i.e., decreasing,
∴ f (x) is decreasing. Hence, f is increasing on (0, π/2) and strictly decreasing on (π/2, π).

Ex 6.2 Class 12 Maths Question 17.
Prove that the function f given by f(x) = log cos x is strictly decreasing on \left( 0,\frac { \pi }{ 2 } \right)  and strictly increasing on \left( \frac { \pi }{ 2 } ,\pi \right)
Solution:
f(x)=log\quad cosx
f’ (x) = \frac { 1 }{ cosx } (-sinx)=-tanx
In the interval \left( 0,\frac { \pi }{ 2 } \right)  ,f’ (x) = -ve
∴ f is strictly decreasing.
In the interval \left( \frac { \pi }{ 2 } ,\pi \right) , f’ (x) is + ve.
∴ f is strictly increasing in the interval.

Ex 6.2 Class 12 Maths Question 18.
Prove that the function given by
f (x) = x3 – 3x2 + 3x -100 is increasing in R.
Solution:
f’ (x) = 3x2 – 6x + 3
= 3 (x2 – 2x + 1)
= 3 (x -1 )2
Now x ∈ R, f'(x) = (x – 1)2≥0
i.e. f'(x)≥0 ∀ x∈R; hence, f(x) is increasing on R.

Ex 6.2 Class 12 Maths Question 19.
The interval in which y = x2 e-x is increasing is
(a) (-∞,∞)
(b) (-2,0)
(c) (2,∞)
(d) (0,2)
Solution:
(d) f’ (x) = 2xe-x + x2( – e-x) = xe-x(2-x) = e-xx(2-x)
Now e-x is positive for all x ∈ R f’ (x) = 0 at x = 0,2
x = 0, x = 2 divide the number line into three disjoint intervals, viz. (-∞, 0), (0,2), (2, ∞)
(a) Interval (-∞,0) x is +ve and (2-x) is +ve
∴ f’ (x) = e-xx (2- x)=(+)(-) (+) = -ve
⇒ f is decreasing in (-∞,0)
(b) Interval (0,2) f’ (x) = e-x x (2 – x)
= (+)(+)(+) = +ve
⇒ f is increasing in (0,2)
(c) Interval (2, ∞) f’ (x) = e-x x (2 – x) = (+) (+) (-)
= – ve
⇒ f is decreasing in the interval (2, ∞)

Ex 6.3 Class 12 Maths Question 1.
Find the slope of the tangent to the curve y = 3x4 – 4x at x = 4.
Solution:
The curve is y = 3x4 – 4x
\frac { dy }{ dx } = 12x3 – 4
∴Req. slope = { \left( \frac { dy }{ dx } \right) }_{ x=4 }
= 12 x 43 – 4 = 764.

Ex 6.3 Class 12 Maths Question 2.
Find the slope of the tangent to the curve y=\frac { x-1 }{ x-2 } ,x\neq 2 at x = 10.
Solution:
The curve is y=\frac { x-1 }{ x-2 }
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.3 Q2.1

Ex 6.3 Class 12 Maths Question 3.
Find the slope of the tangent to curve y = x3 – x + 1 at the point whose x-coordinate is 2.
Solution:
The curve is y = x3 – x + 1
\frac { dy }{ dx } = 3x² – 1
∴slope of tangent = { \left( \frac { dy }{ dx } \right) }_{ x=2 }
= 3 x 2² – 1
= 11

Ex 6.3 Class 12 Maths Question 4.
Find the slope of the tangent to the curve y = x3 – 3x + 2 at the point whose x-coordinate is 3.
Solution:
The curve is y = x3 – 3x + 2
\frac { dy }{ dx } = 3x² – 3
∴slope of tangent = { \left( \frac { dy }{ dx } \right) }_{ x=3 }
= 3 x 3² – 3
= 24

Ex 6.3 Class 12 Maths Question 5.
Find the slope of the normal to the curve x = a cos3 θ, y = a sin3 θ at θ = \frac { \pi }{ 4 }  .
Solution:
\frac { dx }{ d\theta } =-3a\quad { cos }^{ 2 }\theta sin\theta ,\frac { dy }{ d\theta } =3a\quad { sin }^{ 2 }\theta cos\theta
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.3 Q5.1

Ex 6.3 Class 12 Maths Question 6.
Find the slope of the normal to the curve x = 1 – a sin θ, y = b cos² θ at θ = \frac { \pi }{ 2 }
Solution:
\frac { dx }{ d\theta } =-a\quad cos\theta \quad \& \quad \frac { dy }{ d\theta } =2b\quad cos\theta (-sin\theta )
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.3 Q6.1

Ex 6.3 Class 12 Maths Question 7.
Find points at which the tangent to the curve y = x3 – 3x2 – 9x + 7 is parallel to the x-axis.
Solution:
Differentiating w.r.t. x; \frac { dy }{ dx } = 3 (x – 3) (x + 1)
Tangent is parallel to x-axis if the slope of tangent = 0
or \frac { dy }{ dx }=0
⇒3(x + 3)(x + 1) = 0
⇒x = -1, 3
when x = -1, y = 12 & When x = 3, y = – 20
Hence the tangent to the given curve are parallel to x-axis at the points (-1, -12), (3, -20)

Ex 6.3 Class 12 Maths Question 8.
Find a point on the curve y = (x – 2)² at which the tangent is parallel to the chord joining the points (2,0) and (4,4).
Solution:
The equation of the curve is y = (x – 2)²
Differentiating w.r.t x
\frac { dy }{ dx }=2(x-2)
The point A and B are (2,0) and (4,4) respectively.
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.3 Q8.1
Slope of AB = \frac { { y }_{ 2 }-{ y }_{ 1 } }{ { x }_{ 2 }-{ x }_{ 1 } } =\frac { 4-0 }{ 4-2 } =\frac { 4 }{ 2 }  = 2 …(i)
Slope of the tangent = 2 (x – 2) ….(ii)
from (i) & (ii) 2 (x – 2)=2
∴ x – 2 = 1 or x = 3
when x = 3,y = (3 – 2)² = 1
∴ The tangent is parallel to the chord AB at (3,1)

Ex 6.3 Class 12 Maths Question 9.
Find the point on the curve y = x3 – 11x + 5 at which the tangent is y = x – 11.
Solution:
Here, y = x3 – 11x + 5
⇒ \frac { dy }{ dx } = 3x² – 11
The slope of tangent line y = x – 11 is 1
∴ 3x² – 11 = 1
⇒ 3x² = 12
⇒ x² = 4, x = ±2
When x = 2, y = – 9 & when x = -2,y = -13
But (-2, -13) does not lie on the curve
∴ y = x – 11 is the tangent at (2, -9)

Ex 6.3 Class 12 Maths Question 10.
Find the equation of all lines having slope -1 that are tangents to the curve y=\frac { 1 }{ x-1 }, x≠1
Solution:
Here
y=\frac { 1 }{ x-1 }
⇒ \frac { dy }{ dx } =\frac { -1 }{ { (x-1) }^{ 2 } }
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.3 Q10.1

Ex 6.3 Class 12 Maths Question 11.
Find the equation of ail lines having slope 2 which are tangents to the curve y=\frac { 1 }{ x-3 }, x≠3.
Solution:
Here
y=\frac { 1 }{ x-3 }
\frac { dy }{ dx } ={ (-1)(x-3) }^{ -2 }=\frac { -1 }{ { (x-3) }^{ 2 } }
∵ slope of tangent = 2
\frac { -1 }{ { (x-3) }^{ 2 } } =2\Rightarrow { (x-3) }^{ 2 }=-\frac { 1 }{ 2 }
Which is not possible as (x – 3)² > 0
Thus, no tangent to y=\frac { 1 }{ x-3 } has slope 2.

Ex 6.3 Class 12 Maths Question 12.
Find the equations of all lines having slope 0 which are tangent to the curve y=\frac { 1 }{ { x }^{ 2 }-2x+3 }
Solution:
Let the tangent at the point (x1, y1) to the curve
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.3 Q12.1

Ex 6.3 Class 12 Maths Question 13.
Find points on the curve \frac { { x }^{ 2 } }{ 9 } +\frac { { y }^{ 2 } }{ 16 } =1 at which the tangents are
(a) parallel to x-axis
(b) parallel to y-axis
Solution:
The equation of the curve is \frac { { x }^{ 2 } }{ 9 } +\frac { { y }^{ 2 } }{ 16 } =1…(i)
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.3 Q13.1

Ex 6.3 Class 12 Maths Question 14.
Find the equations of the tangent and normal to the given curves at the indicated points:
(i) y = x4 – 6x3 + 13x2 – 10x + 5 at (0,5)
(ii) y = x4 – 6x3 + 13x2 – 10x + 5 at (1,3)
(iii) y = x3 at (1, 1)
(iv) y = x2 at (0,0)
(v) x = cos t, y = sin t at t = \frac { \pi }{ 4 }
Solution:
\frac { dy }{ dx } ={ 4x }^{ 3 }-18{ x }^{ 2 }+26x-10
Putting x = 0, \frac { dy }{ dx }  at (0,5) = – 10
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.3 Q14.1
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.3 Q14.2

Ex 6.3 Class 12 Maths Question 15.
Find the equation of the tangent line to the curve y = x2 – 2x + 7 which is
(a) parallel to the line 2x – y + 9 = 0
(b) perpendicular to the line 5y – 15x = 13.
Solution:
Equation of the curve is y = x² – 2x + 7 …(i)
\frac { dy }{ dx }  = 2x – 2 = 2(x – 1)
(a) Slope of the line 2x – y + 9 = 0 is 2
⇒ Slope of tangent = \frac { dy }{ dx }  = 2(x – 1) = 2
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.3 Q15.1

Ex 6.3 Class 12 Maths Question 16.
Show that the tangents to the curve y = 7x3 + 11 at the points where x = 2 and x = – 2 are parallel.
Solution:
Here, y = 7x3 + 11
=> x \frac { dy }{ dx } = 21 x²
Now m1 = slope at x = 2 is { \left( \frac { dy }{ dx } \right) }_{ x=2 } = 21 x 2² = 84
and m2 = slope at x = -2 is { \left( \frac { dy }{ dx } \right) }_{ x=-2 } = 21 x (-2)² = 84
Hence, m1 = m2 Thus, the tangents to the given curve at the points where x = 2 and x = – 2 are parallel

Ex 6.3 Class 12 Maths Question 17.
Find the points on the curve y = x3 at which the slope of the tangent is equal to the y-coordinate of the point
Solution:
Let P (x1, y1) be the required point.
The given curve is: y = x3
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.3 Q17.1

Ex 6.3 Class 12 Maths Question 18.
For the curve y = 4x3 – 2x5, find all the points at which the tangent passes through the origin.
Solution:
Let (x1, y1) be the required point on the given curve y = 4x3 – 2x5, then y1 = 4x13 – 2x15 …(i)
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.3 Q18.1

Ex 6.3 Class 12 Maths Question 19.
Find the points on the curve x2 + y2 – 2x – 3 = 0 at which the tangents are parallel to the x-axis.
Solution:
Here, x2 + y2 – 2x – 3 = 0
=> \frac { dy }{ dx } =\frac { 1-x }{ y }
Tangent is parallel to x-axis, if \frac { dy }{ dx }=0 i.e.
if 1 – x = 0
⇒ x = 1
Putting x = 1 in (i)
⇒ y = ±2
Hence, the required points are (1,2), (1, -2) i.e. (1, ±2).

Ex 6.3 Class 12 Maths Question 20.
Find the equation of the normal at the point (am2, am3) for the curve ay2 = x3.
Solution:
Here, ay2 = x3
2ay\frac { dy }{ dx } ={ 3x }^{ 2 }\Rightarrow \frac { dy }{ dx } =\frac { { 3x }^{ 2 } }{ 2ay }
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.3 Q20.1

Ex 6.3 Class 12 Maths Question 21.
Find the equation of the normal’s to the curve y = x3 + 2x + 6 which are parallel to the line x + 14y + 4 = 0.
Solution:
Let the required normal be drawn at the point (x1, y1)
The equation of the given curve is y = x3 + 2x + 6 …(i)
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.3 Q21.1

Ex 6.3 Class 12 Maths Question 22.
Find the equations of the tangent and normal to the parabola y² = 4ax at the point (at²,2at).
Solution:
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.3 Q22.1

Ex 6.3 Class 12 Maths Question 23.
Prove that the curves x = y² and xy = k cut at right angles if 8k² = 1.
Solution:
The given curves are x = y² …(i)
and xy = k …(ii)
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.3 Q23.1

Ex 6.3 Class 12 Maths Question 24.
Find the equations of the tangent and normal to the hyperbola \frac { { x }^{ 2 } }{ { a }^{ 2 } } -\frac { { y }^{ 2 } }{ { b }^{ 2 } } =1 at the point (x0 ,y0).
Solution:
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.3 Q24.1

Ex 6.3 Class 12 Maths Question 25.
Find the equation of the tangent to the curve y=\sqrt { 3x-2 }  which is parallel to the line 4x – 2y + 5 = 0.
Solution:
Let the point of contact of the tangent line parallel to the given line be P (x1, y1) The equation of the curve is y=\sqrt { 3x-2 }
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.3 Q25.1

Choose the correct answer in Exercises 26 and 27.

Ex 6.3 Class 12 Maths Question 26.
The slope of the normal to the curve y = 2x² + 3 sin x at x = 0 is
(a) 3
(b) \frac { 1 }{ 3 }
(c) -3
(d) -\frac { 1 }{ 3 }
Solution:
(d) ∵ y = 2x² + 3sinx
\frac { dy }{ dx }=4x+3cosx at
x = 0,\frac { dy }{ dx }=3
∴ slope = 3
⇒ slope of normal is = \frac { 1 }{ 3 }

Ex 6.3 Class 12 Maths Question 27.
The line y = x + 1 is a tangent to the curve y² = 4x at the point
(a) (1,2)
(b) (2,1)
(c) (1,-2)
(d) (-1,2)
Solution:
(a) The curve is y² = 4x,
∴ \frac { dy }{ dx } =\frac { 4 }{ 2y } =\frac { 2 }{ y }
Slope of the given line y = x + 1 is 1 ∴ \frac { 2 }{ y }=1
y = 2 Putting y= 2 in y² = 4x 2² = 4x
⇒ x = 1
∴ Point of contact is (1,2)

Ex 6.5 Class 12 Maths Question 1.
Find the maximum and minimum values, if any, of the following functions given by
(i) f(x) = (2x – 1)² + 3
(ii) f(x) = 9x² + 12x + 2
(iii) f(x) = – (x – 1)² + 10
(iv) g(x) = x3 + 1
Solution:
(i) Minimum value of (2x – 1)² is zero.
Minimum value of (2x – 1)² + 3 is 3
Clearly it does not have maximum value,
(ii) f(x) = 9x² + 12x + 2
⇒ f(x) = (3x + 2)² – 2
Minimum value of (3 + 2)² is zero.
∴ Min.value of (3x + 2)² – 2 = 9x² + 12x + 2 is – 2
f (x) does not have finite maximum value
(iii) f(x) = – (x – 1)² + 10
Maximum value of – (x – 1)² is zero
Maximum valuer f f(x) = – (x – 1)² + 10 is 10
f (x) does not have finite minimum value.
(iv) As x—»∞,g(x)—»∞;Also x—»-∞,g(x)—»-∞
Thus there is no maximum or minimum value of f(x)

Ex 6.5 Class 12 Maths Question 2.
Find the maximum and minimum values, if any, of the following functions given by
(i) f(x) = |x + 2| – 1
(ii) g(x) = -|x + 1| + 3
(iii) h (x) = sin 2x + 5
(iv) f(x) = |sin(4x + 3)|
(v) h(x) = x + 1,x∈(-1,1)
Solution:
(i) We have :f(x) = |x + 2 |-1 ∀x∈R
Now |x + 2|≥0∀x∈R
|x + 2| – 1 ≥ – 1 ∀x∈R ,
So -1 is the min. value of f(x)
now f(x) = -1
⇒ |x + 2|-1
⇒ |x + 2| = 0
⇒ x = – 2
(ii) We have g(x) = -|x + 1| + 3 ∀x∈R
Now | x + 1| ≥ 0 ∀x∈R
-|x+ 1| + 3 ≤3 ∀x∈R
So 3 is the minimum value of f(x).
Now f(x) = 3
⇒ -|x+1| + 3
⇒ |x+1| = 0
⇒ x = – 1.
(iii) Thus maximum value of f(x) is 6 and minimum value is 4.
(iv) Let f(x) = |sin4x + 3|
Maximum value of sin 4x is 1
∴ Maximum value of |sin(4x+3)| is |1+3| = 4
Minimum value of sin 4x is -1
∴ Minimum value of f(x) is |-1+3| = |2|= 2
(v) Greatest value of f (x) is 2 and least value is 0.

Ex 6.5 Class 12 Maths Question 3.
Find the local maxima and local minima, if any, of the following functions. Find also the local maximum and the local minimum values, as the case may be:
(i) f(x) = x2
(ii) g(x) = x3 – 3x
(iii) h(x) = sinx+cosx,0<x<\frac { \pi }{ 4 }
(iv) f(x) = sin4x + cos4x,0<x<\frac { \pi }{ 2 }
(v) f(x) = x– 6x2 + 9x:+15
(vi) g(x) = \frac { x }{ 2 } +\frac { 2 }{ x } , x>0
(vii) g(x) = \frac { 1 }{ { x }^{ 2 }+2 } , x>0
(viii) f(x) = x\sqrt { 1-x } , x>0
Solution:
(i) Let f(x) = x² ⇒ f’(x) = 2x
Now f'(x) = 0 ⇒ 2x = 0 i.e., x = 0
At x = 0; When x is slightly < 0, f’ (x) is -ve When x is slightly > 0, f(x) is +ve
∴ f(x) changes sign from -ve to +ve as x increases through 0.
⇒ f’ (x) has a local minimum at x = 0 local minimum value f(0) = 0.
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.5 Q3.1
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.5 Q3.2
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.5 Q3.3
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.5 Q3.4
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.5 Q3.5
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.5 Q3.6

Ex 6.5 Class 12 Maths Question 4.
Prove that the following functions do not have maxima or minima:
(i) f(x) = ex
(ii) f(x) = log x
(iii) h(x) = x3 + x2 + x + 1
Solution:
(i) f'(x) = ex;
Since f’ (x) ≠ 0 for any value of x.
So f(x) = ex does not have a max. or min.
(ii) f’ (x) = \frac { 1 }{ x }; Clearly f’ (x) ≠ 0 for any value of x.
So,f’ (x) = log x does not have a maximum or a minimum.
(iii) We have f(x) = x3 + x2 + x + 1
⇒f’ (x) = 3x2 + 2x + 1
Now, f’ (x) = 0 => 3x2 + 2x + 1 = 0
x=\frac { -2\pm \sqrt { 4-12 } }{ 6 } =\frac { -1+\sqrt { -2 } }{ 3 }
i.e. f'(x) = 0 at imaginary points
i.e. f'(x) ≠ 0 for any real value of x
Hence, there is neither max. nor min.

Ex 6.5 Class 12 Maths Question 5.
Find the absolute maximum value and the absolute minimum value of the following functions in the given intervals:
(i) f(x) = x3, x∈ [-2,2]
(ii) f(x) = sin x + cos x, x ∈ [0, π]
(iii) f(x) = 4x-\frac { 1 }{ 2 } { x }^{ 2 },x\in \left[ -2,\frac { 9 }{ 2 } \right]
(iv) f(x) = { (x-1) }^{ 2 }+3,x\in \left[ -3,1 \right]
Solution:
(i) We have f’ (x) = x3 in [ -2,2]
∴ f'(x) = 3x²; Now, f’ (x) = 0 at x = 0, f(0) = 0
Now, f(-2) = (-2)3 = – 8; f(0) = (0)² = 0 and f(0) = (2) = 8
Hence, the absolute maximum value of f (x) is 8 which it attained at x = 2 and absolute minimum value of f(x) = – 8 which is attained at x = -2.
(ii) We have f (x) = sin x + cos x in [0, π]
f’ (x) = cos x – sin x for extreme values f’ (x) = 0
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.5 Q5.1

Ex 6.5 Class 12 Maths Question 6.
Find the maximum profit that a company can make, if the profit function is given by p(x) = 41 – 24x – 18x²
Solution:
Profit function in p(x) = 41 – 24x – 18x²
∴ p'(x) = – 24 – 36x = – 12(2 + 3x)
for maxima and minima, p'(x) = 0
Now, p'(x) = 0
⇒ – 12(2 + 3x) = 0
⇒ x = -\frac { 2 }{ 3 },
p'(x) changes sign from +ve to -ve.
⇒ p (x) has maximum value at x = -\frac { 2 }{ 3 }
Maximum Profit = 41 + 16 – 8 = 49.

Ex 6.5 Class 12 Maths Question 7.
Find both the maximum value and the minimum value of 3x4 – 8x3 + 12x2 – 48x + 25 on the interval [0,3].
Solution:
Let f(x) = 3x4 – 8x3 + 12x2 – 48x + 25
∴f'(x) = 12x3 – 24x2 + 24x – 48
= 12(x2 + 2)(x – 2)
For maxima and minima, f'(x) = 0
⇒ 12(x2 + 2)(x – 2) = 0
⇒ x = 2
Now, we find f (x) at x = 0,2 and 3, f (0) = 25,
f (2) = 3 (24) – 8 (23) + 12 (22) – 48 (2) + 25 = – 39
and f (3) = (34) – 8 (33) + 12 (32) – 48 (3) + 25
= 243 – 216 + 108 – 144 + 25 = 16
Hence at x = 0, Maximum value = 25
at x = 2, Minimum value = – 39.

Ex 6.5 Class 12 Maths Question 8.
At what points in the interval [0,2π], does the function sin 2x attain its maximum value?
Solution:
We have f (x) = sin 2x in [0,2π], f’ (x) = 2 cos 2 x
For maxima and minima f’ (x) = 0 => cos 2 x = 0
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.5 Q8.1

Ex 6.5 Class 12 Maths Question 9.
What is the maximum value of the function sin x + cos x?
Solution:
Consider the interval [0, 2π],
Let f(x) = sinx + cosx,
f’ (x) = cosx – sinx
For maxima and minima, f’ (x) = 0
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.5 Q9.1

Ex 6.5 Class 12 Maths Question 10.
Find the maximum value of 2x3 – 24x + 107 in the interval [1,3]. Find the maximum value of the same function in [-3, -1].
Solution:
∵ f(x) = 2x3 – 24x + 107
∴f(x) = 6x2 – 24 ,
For maxima and minima f'(x) = 0;⇒ x = ±2
For the interval [ 1,3], we find the values of f (x)
at x = 1,2,3; f(1) = 85, f(2) = 75, f(3) = 89
Hence, maximum f (x) = 89 at x = 3
For the interval [-3, -1], we find the values of f(x) at x = – 3, – 2, – 1;
f(-3) = 125;
f(-2) = 139
f(-1) = 129
∴ max.f(x) = 139 at x = – 2.

Ex 6.5 Class 12 Maths Question 11.
It is given that at x = 1, the function x4 – 62x2 + ax + 9 attains its maximum value, on the interval [0,2]. Find the value of a.
Solution:
∵ f(x) = x4 – 62x2 + ax + 9
∴ f’ (x) = 4x3 – 124x + a
Now f’ (x) = 0 at x = 1
⇒ 4 – 124 + a = 0
⇒ a = 120
Now f” (x) = 12x2 – 124:
At x = 1 f” (1) = 12 – 124 = – 112 < 0
⇒ f(x) has a maximum at x = 1 when a = 120.

Ex 6.5 Class 12 Maths Question 12.
Find the maximum and minimum values of x + sin 2x on [0,2π]
Solution:
∴f(x) = x + sin2x on[0,2π]
∴f’ (x) = 1+2 cos2x
For maxima and minima f’ (x) = 0
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.5 Q12.1

Ex 6.5 Class 12 Maths Question 13.
Find two numbers whose sum is 24 and whose product is as large as possible.
Solution:
Let the required numbers hex and (24-x)
∴Their product,p = x(24 – x) = 24x – x²
Now \frac { dp }{ dx } = 0 ⇒24 – 2x = 0 ⇒ x = 12
Also \frac { { d }^{ 2 }p }{ { dx }^{ 2 } }  = -2<0: ⇒ p is max at x = 12
Hence, the required numbers are 12 and (24-12)i.e. 12.

Ex 6.5 Class 12 Maths Question 14.
Find two positive numbers x and y such that x + y = 60 and xy3 is maximum.
Solution:
We have x + y = 60
⇒ y = 60 – x …(i)
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.5 Q14.1
Hence, the req. numbers are 15 and (60 -15) i.e. 15 and 45.

Ex 6.5 Class 12 Maths Question 15.
Find two positive numbers x and y such that their sum is 35 and the product x2 y5 is a maximum.
Solution:
We have x + y = 35 ⇒ y = 35 – x
Product p = x2 y5
= x2 (35 – x)5
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.5 Q15.1

Ex 6.5 Class 12 Maths Question 16.
Find two positive numbers whose sum is 16 and the sum of whose cubes is minimum.
Solution:
Let two numbers be x and 16 – x
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.5 Q16.1
Hence, the required numbers are 8 and (16-8) i.e. 8 and 8.

Ex 6.5 Class 12 Maths Question 17.
A square piece of tin of side 18 cm is to be made into a box without top, by cutting a square from each corner and folding up the flaps to form the box. What should be the side of the square to be cut off so that the volume of the box is the maximum possible.
Solution:
Let each side of the square to be cut off be x cm.
∴ for the box length = 18 – 2x: breadth = 18 – 2x and height = x
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.5 Q17.1

Ex 6.5 Class 12 Maths Question 18.
A rectangular sheet of tin 45 cm by 24 cm is to be made into a box without top, by cutting off square from each comer and folding up the flaps. What should be the side of the square to be cut off so that the volume of the box is maximum?
Solution:
Let each side of the square cut off from each comer be x cm.
∴ Sides of the rectangular box are (45 – 2x), (24 – 2x) and x cm.
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.5 Q18.1

Ex 6.5 Class 12 Maths Question 19.
Show that of all the rectangles inscribed in a given fixed circle, the square has the maximum area.
Solution:
Let the length and breadth of the rectangle inscribed in a circle of radius a be x and y respectively.
∴ x² + y² = (2a)² => x² + y² = 4a² …(i)
∴ Perimeter = 2 (x + y)
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.5 Q19.1

Ex 6.5 Class 12 Maths Question 20.
Show that the right circular cylinder of given surface and maximum volume is such that its height is equal to the diameter of the base.
Solution:
Let S be the given surface area of the closed cylinder whose radius is r and height h let v be the its Volume. Then
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.5 Q20.1

Ex 6.5 Class 12 Maths Question 21.
Of all the closed cylindrical cans (right circular), of a given volume of 100 cubic centimeters, find the dimensions of the can which has the minimum surface area ?
Solution:
Let r be the radius and h be the height of cylindrical can.
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.5 Q21.1

Ex 6.5 Class 12 Maths Question 22.
A wire of length 28 m is to be cut into two pieces. One of the pieces is to be made into a square and the other into a circle. What should be the length of the two pieces so that the combined area of the square and the circle is minimum ?
Solution:
Let one part be of length x, then the other part = 28 – x
Let the part of the length x be converted into a circle of radius r.
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.5 Q22.1
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.5 Q22.2
Ex 6.5 Class 12 Maths Question 23.
Prove that the volume of the largest cone that can be inscribed in a sphere of radius R is \frac { 8 }{ 27 } of the volume of the sphere.
Solution:
Let a cone. VAB of greatest volume be inscribed in the sphere let AOC = θ
∴ AC, radius of the base of the cone = R sin θ
and VC = VO + OC = R(1 +cosθ)
= R + Rcosθ
= height of the cone.,
V, the volume of the cone.
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.5 Q23.1
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.5 Q23.2

Ex 6.5 Class 12 Maths Question 24.
Show that die right circular cone of least curved surface and given volume has an altitude equal to √2 time the radius of the base.
Solution:
Let r and h be the radius and height of the cone.
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.5 Q24.1

Ex 6.5 Class 12 Maths Question 25.
Show that the semi-vertical angle of the cone of the maximum volume and of given slant height is tan-1 √2.
Solution:
Let v be the volume, l be the slant height and 0 be the semi vertical angle of a cone.
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.5 Q25.1

Ex 6.5 Class 12 Maths Question 26.
Show that semi-vertical angle of right circular cone of given surface area and maximum volume is { sin }^{ -1 }\left( \frac { 1 }{ 3 } \right)
Solution:
Let r be radius, l be the slant height and h be the height of the cone of given surface area s.Then
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.5 Q26.1
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.5 Q26.2

Choose the correct answer in the Exercises 27 and 29.

Ex 6.5 Class 12 Maths Question 27.
The point on die curve x² = 2y which is nearest to the point (0,5) is
(a) (2 √2,4)
(b) (2 √2,0)
(c) (0,0)
(d) (2,2)
Solution:
(a) Let P (x, y) be a point on the curve The other point is A (0,5)
Z = PA² = x² + y² + 25 – 10y [∵ x² = 2y]
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.5 Q27.1

Ex 6.5 Class 12 Maths Question 28.
For all real values of x, the minimum value of \frac { 1-x+{ x }^{ 2 } }{ 1+x+{ x }^{ 2 } }
(a) 0
(b) 1
(c) 3
(d) \frac { 1 }{ 3 }
Solution:
(d) Let y=\frac { 1-x+{ x }^{ 2 } }{ 1+x+{ x }^{ 2 } }
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.5 Q28.1

Ex 6.5 Class 12 Maths Question 29.
The maximum value of { \left[ x\left( x-1 \right) +1 \right] }^{ \frac { 1 }{ 3 } },0\le x\le 1 is
(a) { \left( \frac { 1 }{ 3 } \right) }^{ \frac { 1 }{ 3 } }
(b) \frac { 1 }{ 2 }
(c) 1
(d) 0
Solution:
(c) Let y = { \left[ x\left( x-1 \right) +1 \right] }^{ \frac { 1 }{ 3 } },0\le x\le 1
NCERT Solutions for Class 12 Maths Chapter 6 Application of Derivatives Ex 6.5 Q29.1

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NCERT MCQ CLASS-12 CHAPTER-10 | CHEMISTRY NCERT MCQ | HALOALKANES AND HALOARENES | EDUGROWN

In This Post we are  providing Chapter-10 Haloalkanes and Haloarenes  NCERT MCQ for Class 12 Chemistry which will be beneficial for students. These solutions are updated according to 2021-22 syllabus. These MCQS  can be really helpful in the preparation of Board exams and will provide you with a brief knowledge of the chapter.

NCERT MCQ ON HALOALKANES AND HALOARENES

Question 1.
Good conductor of electricity and heat is

(a) Anthracite coke
(b) Diamond
(c) Graphite
(d) Charcoal

Answer: (c) Graphite

Question 2.
In which of the following allotropes of carbon, percentage of carbon is maximum?

(a) Wood charcoal
(b) Coconut charcoal
(c) Graphite
(d) None of these

Answer: (c) Graphite

Question 3.
The hybridization of carbon in diamond is

(a) sp3
(b) sp2
(c) sp
(d) dsp2Answer

Answer: (a) sp3

Question 4.
Organic compound must contain an element

(a) oxygen
(b) carbon
(c) hydrogen
(d) nitrogen

Answer: (b) carbon

Question 5.
Alkene gives which of the following reactions?

(a) Addition reaction
(b) Substitution reaction
(c) Both (a) and (b)
(d) None of these

Answer: (c) Both (a) and (b)

Question 6.
Single bond length between carbon-carbon is

(a) 1.34 Å
(b) 1.20 Å
(c) 1.54 Å
(d) none of these

Answer: (c) 1.54 Å

Question 7.
Valency of carbon is

(a) 1
(b) 2
(c) 3
(d) 4

Answer: (d) 4

Question 8.
Criteria for purity of organic solid is

(a) boiling point
(b) melting point
(c) specific gravity
(d) none of these

Answer: (b) melting point

Question 9.
General formula of Alkene is

(a) CnH2n
(b) CnH2n+2
(c) CnH2n-2
(d) none of these

Answer: (a) CnH2n

Question 10.
Hybridization of carbon in ethane is

(a) sp3
(b) sp2
(c) sp
(d) sp3d2

Answer: (a) sp3

Question 11.
Number of π bonds in ethyne is

(a) 1
(b) 2
(c) 3
(d) 4

Answer: (b) 2

Question 12.
The compound having general formula CnH2n+2 is

(a) Alkene
(b) Alkyne
(c) Alkane
(d) none of these

Answer: (c) Alkane

Question 13.
Which of the following is not correctly matched with its IUPAC name?

(a) CHF2CBrClF : 1-Bromo-1-chIoro-1, 2, 2-trifluoroethane
(b) (CCl3)3CCl : 2-(Trichloromethyl)-1, 1, 2, 3, 3-heptachloropropane
(c) CH3C (p-ClC6H4)2CH(Br)CH3 : 2-Bromo-3, 3-bis (4- chlorophenyl) butane
(d) o-BrC6H4CH (CH3) CH2CH3 : 2-Bromo-l- methylpropylbenzene

Answer: (b) (CCl3)3CCl : 2-(Trichloromethyl)-1, 1, 2, 3, 3-heptachloropropane

Question 14.
The negative part of the addendum (the molecule to be added) adds on the carbon atom of the double bond containing the least number of hydrogen atoms. This rule is known as

(a) Saytzeffs rule
(b) Peroxide rule
(c) Markovnikov’s rule
(d) Van’t Hoff rule

Answer: (c) Markovnikov’s rule

Question 15.
Which of the following compounds can yield only one monochlorinated product upon free radical chlorination?

(a) 2, 2-Dimethylpropane
(b) 2-Methylpropane
(c) 2-Methylbutane
(d) n-Butane

Answer: (a) 2, 2-Dimethylpropane


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