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NCERT Solutions for Exercise 7.3 Class 12 Maths Chapter 7 - Integrals

NCERT Solutions for Exercise 7.3 Class 12 Maths Chapter 7 - Integrals

Edited By Ramraj Saini | Updated on Dec 03, 2023 09:49 PM IST | #CBSE Class 12th

NCERT Solutions For Class 12 Maths Chapter 7 Exercise 7.3

NCERT Solutions for Exercise 7.3 Class 12 Maths Chapter 7 Integrals are discussed here. These NCERT solutions are created by subject matter expert at Careers360 considering the latest syllabus and pattern of CBSE 2023-24. NCERT solutions for Class 12 Maths chapter 7 exercise 7.3 is another exercise of the NCERT syllabus chapter integrals. It exposes students to some higher level of problems of integrals which includes complex trigonometric functions. Exercise 7.3 Class 12 Maths can be directly solved by students here only to understand the concepts well. NCERT Solutions for Class 12 Maths chapter 7 exercise 7.3 provided below are holistic in nature and have been prepared by experienced faculties. NCERT solutions for exercise 7.3 Class 12 Maths chapter 7 cannot be neglected to perform better in exams like JEE Main.

12th class Maths exercise 7.3 answers are designed as per the students demand covering comprehensive, step by step solutions of every problem. Practice these questions and answers to command the concepts, boost confidence and in depth understanding of concepts. Students can find all exercise together using the link provided below.

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Integrals Class 12 Chapter 7 Exercise: 7.3

Question:1 Find the integrals of the functions \sin ^ 2 ( 2x+ 5 )

Answer:

\sin ^ 2 ( 2x+ 5 )

using the trigonometric identity

sin^2x=\frac{1-cos2x}{2}

we can write the given question as

= \frac{1-\cos 2(2x+5)}{2} = \frac{1-\cos (4x+10)}{2}
\\=\int \frac{1-\cos (4x+10)}{2}dx\\ =\frac{1}{2}\int dx - \frac{1}{2}\int \cos(4x+10)dx\\ =\frac{x}{2}-\frac{1}{2}[\sin(4x+10)/4]\\ =\frac{x}{2}-\frac{\sin(4x+10)}{8}+C

Question:2 Find the integrals of the functions \sin 3x \cos 4x

Answer:

Using identity \sin A\cos B = 1/2[sin(A+B)+sin(A-B)]

, therefore the given integral can be written as

\int \sin 3x\cos 4x=\frac{1}{2}\int sin(3x+4x)+sin(3x-4x)\ dx

=\frac{1}{2}\int sin(7x)-sin(x)\ dx\\ =1/2[\int \sin (7x) dx-\int \sin x\ dx]\\ =\frac{1}{2}[(-1/7)\cos 7x+\cos x+ C]\\ = \frac{\cos x}{2}-\frac{\cos 7x}{14}+C

Question:3 Find the integrals of the functions \cos 2x \cos 4x \cos 6x

Answer:

Using identity
cosAcosB = \frac{1}{2}[cos(A+B)+cos(A-B)]

\int \cos 2x.\cos 4x.\cos 6x = \int \cos 2x. \frac{1}{2}[(\cos 10x)+\cos 2x]dx

Again use the same identity mentioned in the first line

\\= \frac{1}{2}\int (\cos 2x.\cos 10x+\cos 2x. \cos 2x)dx\\ =\frac{1}{2}\int\frac{1}{2}({\cos12x +\cos 8x})dx+\frac{1}{2}\int (\frac{1+\cos 4x}{2})dx\\ =\frac{\sin 12x}{48}+\frac{\sin 8x}{32}+\frac{\sin 4x}{16}+ x/4+C

Question:4 Find the integrals of the functions \sin ^ 3 ( 2x +1 )

Answer:

\int \sin^3(2x+1)dx = \int \sin^2(2x+1).\sin(2x+1)dx

The integral can be written as

= \int (1-\cos^2(2x+1)).\sin(2x+1)dx
Let
\\\cos (2x+1) =t\\ \sin (2x+1)dx = -dt/2

\\=\frac{-1}{2}\int (1-t^2)dt\\ =\frac{-1}{2}[t-t^3/3]\\ =\frac{t^3}{6}-\frac{t}{2}

Now, replace the value of t, we get;

=\frac{\cos^3(2x+1)}{6}-\frac{\cos(2x+1)}{2}+C

Question:5 Find the integrals of the functions \sin ^3 x \cos ^ 3 x

Answer:

I = \int \sin^3x.\cos^3x\ dx

rewrite the integral as follows

\\=\int cos^3x.sin^2x.\sin x\ dx\\ =\int cos^3x(1-\cos^2x)\sin x\ dx
Let \cos x = t \Rightarrow \sin x dx =-dt

\\=-\int t^3(1-t^2)dt\\ =-\int(t^3-t^5)dt\\ =-[\frac{t^4}{4}]+[\frac{t^6}{6}] +C\\ =\frac{\cos^6x}{6}-\frac{cos^4x}{4}+C ......(replace the value of t as cos\ x )

Question:6 Find the integrals of the functions \sin x \sin 2x \sin 3x

Answer:

Using the formula
sinAsinB=\frac{1}{2}(cos(A-B)-cos(A+B))

we can write the integral as follows

\int \sin x.\sin 2x\sin 3x\ dx = \int \sin x\frac{1}{2}[\cos x-\cos 5x]dx
\\=\frac{1}{2} \int [\sin x.\cos x-\sin x.\cos 5x]dx\\ =\frac{1}{2}\int \frac{\sin 2x}{2}dx-\frac{1}{2}\int \sin x. \cos 5x\ dx\\ =-\frac{\cos 2x}{8}-\frac{1}{4}\int[\sin 6x -\sin 4x]\\ =-\frac{\cos 2x}{8}-\frac{1}{4}[\frac{-\cos 6x}{6}+\frac{\cos 4x}{4}]\\ =-\frac{\cos 2x}{8}+\frac{\cos 6x}{24}-\frac{\cos 4x}{16}+C

Question:7 Find the integrals of the functions \sin 4x \sin 8x

Answer:

Using identity

sinAsinB=\frac{1}{2}(cos(A-B)-cos(A+B))

we can write the following integral as

\sin 4x \sin 8x =
\\=\frac{1}{2}\int(\cos 4x - \cos 12x) dx\\ =\frac{1}{2} [\int\cos 4x\ dx - \int \cos 12x\ dx]\\ =\frac{\sin 4x}{8}-\frac{\sin 12x}{24}+C

Question:8 Find the integrals of the functions \frac{1- \cos x }{1+ \cos x }

Answer:

We know the identities

\\1+\cos 2A = 2\cos^2A\\ 1-\cos 2A = 2\sin^2 A

Using the above relations we can write

\frac{1-\cos x}{1+\cos x}=\frac{\sin^2x/2}{\cos^2x/2} = \tan^2x/2

=\int \tan^2x/2 =\int (\sec^2x/2-1)dx
\\=\int (\sec^2x/2)dx-\int dx\\ = 2[\tan x/2]-{x}+C

Question:9 Find the integrals of the functions \frac {\cos x }{1 + \cos x }

Answer:

The integral is rewritten using trigonometric identities

\frac{\cos x}{1+ \cos x}= \frac{\cos^2x/2-\sin^2x/2}{2\cos^2x/2} =\frac{1}{2}[1-\tan^2x/2]
\\=\int \frac{1}{2}[1-\tan^2x/2] dx\\ =\frac{1}{2}\int 1-[sec^2\frac{x}{2}-1]=\frac{1}{2}\int 2-sec^2\frac{x}{2}\\=x-tan\frac{x}{2}+c

Question:10 Find the integrals of the functions \sin ^ 4 x

Answer:

\sin ^ 4 x can be written as follows using trigonometric identities
\\=\sin^2x.\sin^2x\\ =\frac{1}{4}(1-\cos 2x)^{2}\\ =\frac{1}{4}(1+\cos^22x-2\cos 2x)\\ =\frac{1}{4}(1+\frac{1}{2}(1+\cos 4x)-2\cos 2x)\\ =3/8+\frac{\cos 4x}{8}-\frac{\cos 2x}{2}

Therefore,
\Rightarrow \int \sin^4x\ dx = \int \frac{3}{8}dx+\frac{1}{8}\int\cos 4x\ dx -\frac{1}{2}\int\cos 2x\ dx
= \frac{3x}{8}+\frac{\sin 4x}{32} -\frac{\sin 2x}{4}+C

Question:11 Find the integrals of the functions \cos ^ 4 2x

Answer:

cos^42x=cos^32xcos2x

now using the identity

cos^3x=\frac{cos3x+3cosx}{4}

cos^32xcos2x=\frac{cos6x +3cos2x}{4}cos2x=\frac{cos6xcos2x+3cos^22x}{4}

now using the below two identities

cosacosb=\frac{cos(a+b)+cos(a-b)}{2}\\and\ cos^22x=\frac{1+cos4x}{2}\\

the value

cos^42x=cos^32xcos2x\\=\frac{cos6xcos2x+3cos^22x}{4}=\frac{cos 4x+cos8x}{8}+\frac{3}{4}\frac{1+cos4x}{2} .

the integral of the given function can be written as

\int cos^42x=\int \frac{cos 4x+cos8x}{8}+\int \frac{3}{4}\frac{1+cos4x}{2}\\ \\=\frac{3}{8}x+\frac{sin4x}{8}+\frac{sin8x}{64}+C

Question:12 Find the integrals of the functions \frac{\sin ^ 2x }{1+ \cos x }

Answer:

Using trigonometric identities we can write the given integral as follows.

\frac{\sin ^ 2x }{1+ \cos x }

\\=\frac{4\sin^2\frac{x}{2}\cos^2\frac{x}{2}}{2\cos^2\frac{x}{2}}\\ =2\sin^2\frac{x}{2}\\ =1-\cos x

\therefore \int \frac{sin^22x}{1+\cos x} = \int (1-\cos x)dx
\\= \int 1dx-\int\cos x\ dx\\ =x-\sin x+C

Question:13 Find the integrals of the functions \frac{\cos 2x - \cos 2 \alpha }{\cos x - \cos \alpha }

Answer:

We know that,

\cos A-\cos B = -2\sin(\frac{A+B}{2})\sin(\frac{A-B}{2})

Using this identity we can rewrite the given integral as

\frac{\cos 2x-\cos 2\alpha }{\cos x-\cos\alpha}=\frac{-2\sin\frac{2x+2\alpha}{2}\sin\frac{2x-2\alpha}{2}}{-2\sin\frac{x+\alpha}{2}\sin\frac{x-\alpha}{2}}

\\=\frac{\sin(x+\alpha)\sin(x-\alpha)}{\sin\frac{x+\alpha}{2}\sin\frac{x-\alpha}{2}}\\ =\frac{[2\sin\frac{x+\alpha}{2}\cos \frac{x+\alpha}{2}][2\sin\frac{x-\alpha}{2}\cos\frac{x-\alpha}{2}]}{\sin\frac{x+\alpha}{2}\sin\frac{x-\alpha}{2}}\\ =4\cos\frac{x+\alpha}{2}\cos\frac{x-\alpha}{2}\\ =2[\cos x+\cos \alpha]

\therefore \int\frac{\cos 2x-\cos 2\alpha }{\cos x-\cos\alpha}=\int 2\cos x\ dx +\int 2\cos \alpha\ dx
=2[\sin x + x\cos \alpha]+C

Question:14 Find the integrals of the functions \frac{\cos x - \sin x }{1+ \sin 2x }

Answer:

\frac{\cos x-\sin x}{1+2\sin x}=\frac{\cos x-\sin x}{(sin^2x+cos^2x)+2 sin x.\cos x}
=\frac{\cos x-\sin x}{(\sin x+\cos x)^2}


\\sin x+\cos x =t\\ \therefore (\cos x-\sin x)dx = dt

Now,
=\int \frac{dt}{t^2}\\ =\int t^-2\ dt\\ =-t^{-1}+C\\ =-\frac{1}{(\sin x+\cos x)}+C

Question:15 Find the integrals of the functions \tan ^ 3 2x \sec 2x

Answer:

\tan^32x.\sec 2x = \tan^22x.\tan 2x.\sec 2x
\\= (\sec^22x-1).\tan 2x.\sec 2x\\ =\sec^22x.\tan 2x-\tan 2x.\sec 2x

Therefore integration of \tan ^ 3 2x \sec 2x =
\\=\int\sec^22x.\tan 2x\ dx-\int\tan 2x.\sec 2x\ dx\\ =\int\sec^22x.\tan 2x\ dx-\sec 2x/2+C\\ .....................(i)
Let assume

\sec 2x = t
So, that 2\sec 2x.\tan 2x\ dx =dt
Now, the equation (i) becomes,

\\\Rightarrow \frac{1}{2}\int t^2\ dt-\frac{\sec 2x}{2}+C\\ \Rightarrow \frac{t^3}{6}-\frac{\sec 2x}{2}+C\\ =\frac{(\sec 2x)^3}{6}-\frac{\sec 2x}{2}+C

Question:16 Find the integrals of the functions \tan ^ 4x

Answer:

the given question can be rearranged using trigonometric identities

tan^4x=(\sec^2x-1).\tan^2x\\ =\sec^2x.\tan^2x-\tan^2x\\ =\sec^2x.\tan^2x-\sec^2x+1

Therefore, the integration of \tan^4x = \\=\int \sec^2x.\tan^2x\ dx-\int\sec^2x\ dx+\int dx\\ =(\int \sec^2x.\tan^2x\ dx)-\tan x+x+C\\ ...................(i)
Considering only \int \sec^2x.\tan^2x\ dx
let \tan x =t\Rightarrow \sec^2x\ dx =dt

\int \sec^2x\tan^2x\ dx = \int t^2\ dt = t^3/3=\frac{\tan^3x}{3}

now the final solution is,

\int \tan^4x =\frac{\tan^3x}{3}-\tan x+x+C

Question:17 Find the integrals of the functions \frac{\sin ^ 3x + \cos ^ 3x }{\sin ^ 2 x \cos ^2 x }

Answer:

\frac{\sin ^ 3x + \cos ^ 3x }{\sin ^ 2 x \cos ^2 x }

now splitting the terms we can write

\\=\frac{\sin^3x}{\sin^2x.\cos^2x}+\frac{\cos^3x}{\sin^2x.\cos^2x}\\ =\frac{\sin x}{cos^2x}+\frac{\cos x}{\sin^2x}\\ =\tan x.\sec x+\cot xcosec x

Therefore, the integration of
\frac{\sin ^ 3x + \cos ^ 3x }{\sin ^ 2 x \cos ^2 x }

\\=\int (\tan x\sec x+\cot xcosec x)dx\\ =\sec x-cosec\ x+C

Question:18 Find the integrals of the functions \frac{\cos 2 x + 2 \sin ^ 2x }{\cos ^ 2 x }

Answer:

The integral of the above equation is

\\=\int (\frac{\cos 2x+2\sin^2x}{\cos^2x})dx\\ =\int (\frac{\cos 2x+(1-\cos 2x)}{\cos^2x}\\ =\int\frac{1}{\cos^2x}\\ =\int \sec^2x\ dx =\tan x+C

Thus after evaluation, the value of integral is tanx+ c

Question:19 Find the integrals of the functions \frac{1}{\sin x \cos ^3 x }

Answer:

Let
We can write 1 = \sin^2x +\cos^2x
Then, the equation can be written as
I =\frac{\sin^2x +\cos^2x}{\sin x\cos^3x}

I =\int (\tan x+\frac{1}{\tan x})\sec^2 x dx
put the value of tan x = t
So, that \sec^2xdx =dt

\\\Rightarrow I=\int (t+\frac{1}{t})dt\\ =\frac{t^2}{2}+\log\left | t \right |+C\\ =\log\left | \tan x \right |+\frac{1}{2}\tan^2x+C

Question:20 Find the integrals of the functions \frac{\cos 2x }{( \cos x + \sin x )^2}

Answer:

we know that cos2x= cos^2x-sin^2x
therefore,

\frac{\cos 2x }{( \cos x + \sin x )^2}
\frac{\cos 2x}{1+\sin 2x}\\ \Rightarrow \int \frac{\cos 2x}{1+\sin 2x}\\ let 1+sin2x =t \Rightarrow 2cos2x\ dx = dt
Now the given integral can be written as

\therefore \int \frac{\cos 2x}{(\cos x+\sin x)^2}=\frac{1}{2}\int \frac{1}{t}dt
\\\Rightarrow \frac{1}{2}\log\left | t \right |+C\\ \Rightarrow \frac{1}{2}\log\left | 1+\sin 2x \right |+C\\=log|sin^2x+cos^2x+2sinxcosx|+C\\=\frac{1}{2}log|(sinx+cosx)^2|+C=log|sinx+cosx|+C

Question:21 Find the integrals of the functions \sin ^ { -1} ( \cos x )

Answer:

using the trigonometric identities we can evaluate the following integral as follows

\dpi{100} \int \sin^{-1}(\cos x)dx = \int \sin^{-1}(sin(\frac{\pi}{2}-x))dx\\=\int(\frac{\pi}{2}-x)dx=\frac{\pi x}{2}-\frac{x^2}{2}+C

Question:22 Find the integrals of the functions \frac{1}{\cos ( x-a ) \cos ( x-b )}

Answer:

Using the trigonometric identities following integrals can be simplified as follows

\frac{1}{\cos(x-a)\cos(x-b)}=\frac{1}{\sin(a-b)}[\frac{\sin(a-b)}{\cos(x-a)\cos(x-b)}]

=\frac{1}{\sin(a-b)}[\frac{\sin[(x-b)-(x-a)]}{\cos(x-a)\cos(x-b)}]

=\frac{1}{\sin(a-b)}[\frac{\sin(x-b)\cos(x-a)-\cos(x-b)\sin(x-a)}{\cos(x-a)\cos(x-b)}]

=\frac{tan(x-b)-\tan (x-a)}{\sin(a-b)}

=\frac{1}{\sin(a-b)}\int tan(x-b)-\tan (x-a)dx
\\=\frac{1}{\sin(a-b)}[-\log\left | \cos(x-b) \right |+\log\left | \cos(x-a) \right |]\\ =\frac{1}{\sin(a-b)}(\log\left | \frac{\cos(x-a)}{\cos(x-b)} \right |)

Question:23 Choose the correct answer

\int \frac{\sin ^ 2 x - \cos ^ 2 x dx }{\sin ^ 2 x \cos ^ 2x } dx \: \:is \: \:equal \: \: to stgdrffd

Answer:

The correct option is (A)

On reducing the above integral becomes \sec^2x-csc^2x
\int\sec^2x-csc^2x\ dx = \tan x+ \cot x+C

Question:24 Choose the correct answer \int \frac{e ^x ( 1+x)}{\cos ^ 2 ( e ^xx )} dx \: \: equals

\\(A) -\cot (ex^x) + C \\\\ (B) \tan (xe^x) + C\\\\ (C) \tan (e^x) + C \\\\ (D) \cot (e^x) + C

Answer:

The correct option is (B)

Let e^xx = t .
So, (e^x.x+ 1.e^x)dx = dt
(1+ x ) e^x\ dx =dt

therefore,

\int \frac{e^x(1+x)}{\cos^2(e^x.x)}dx =\int\frac{dt}{\cos^2t}
\\=\int \sec^2t dt\\ =\tan t +C\\ =\tan(e^x.x)+C



More About NCERT Solutions for Class 12 Maths Chapter 7 Exercise 7.3

The NCERT Class 12 Maths chapter Integrals provided here is of good quality and can be referred by students preparing for various examinations. Exercise 7.3 Class 12 Maths is important for some of the NCERT book Physics topics also. Hence NCERT Solutions for Class 12 Maths chapter 7 exercise 7.3 are good to go for both Maths as well as Physics.

Also Read| Integrals Class 12 Notes

Benefits of NCERT Solutions for Class 12 Maths Chapter 7 Exercise 7.3

  • The Class 12th Maths chapter 7 exercise provided here is of best quality.
  • Students can skip questions from exercise 7.3 Class 12 Maths which are repeated in concept to save their time.
  • These Class 12 Maths chapter 7 exercise 7.3 solutions are helpful for NEET, JEE as well as Board examinations.
  • NCERT Solutions for class 12 maths chapter 7 exercise 7.3 are highly recommended to students. Theory also can be understood with the help of exercise solutions only.
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Key Features Of NCERT Solutions for Exercise 7.3 Class 12 Maths Chapter 7

  • Comprehensive Coverage: The solutions encompass all the topics covered in ex 7.3 class 12, ensuring a thorough understanding of the concepts.
  • Step-by-Step Solutions: In this class 12 maths ex 7.3, each problem is solved systematically, providing a stepwise approach to aid in better comprehension for students.
  • Accuracy and Clarity: Solutions for class 12 ex 7.3 are presented accurately and concisely, using simple language to help students grasp the concepts easily.
  • Conceptual Clarity: In this 12th class maths exercise 7.3 answers, emphasis is placed on conceptual clarity, providing explanations that assist students in understanding the underlying principles behind each problem.
  • Inclusive Approach: Solutions for ex 7.3 class 12 cater to different learning styles and abilities, ensuring that students of various levels can grasp the concepts effectively.
  • Relevance to Curriculum: The solutions for class 12 maths ex 7.3 align closely with the NCERT curriculum, ensuring that students are prepared in line with the prescribed syllabus.

Also see-

NCERT Solutions Subject Wise

Subject Wise NCERT Exemplar Solutions

Happy learning!!!

Frequently Asked Question (FAQs)

1. What are the topics asked in NCERT solutions for Class 12 Maths chapter 7 exercise 7.3 ?

Topics like finding out integrals of trigonometric functions, square root functions etc. are asked in the examination. 

2. Where is the use of Integration ?

Integration can be used to find the area, volume etc. in physics and other disciplines. 

3. Is exercise 7.3 important for Board examinations ?

Yes, it is significant for the board examinations. 5 markers are generally asked from this exercise only. 

4. What is the level of questions in exercise 7.3 class 12 Maths ?

Moderate level of questions are there in this exercise,

5. Is this helpful for Physics Topics also?

Yes, some functions like sinx, cosx etc. are used in physics calculations. Hence can be referred for Physics topics also. 

6. How many questions are there in Class 12th Maths chapter 7 exercise 7.3 ?

In total there are 24 questions in this exercise 

7. Is it necessary to solve every question of the exercise?

No, just try to solve maximum and cover maximum concepts. Some questions which are based on the same concepts can be skipped. 

8. Should I refer to any other book for this chapter for Boards?

No, as NCERT questions are more than sufficient for Boards. You can revise these questions only. 

 

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hello mahima,

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hope this helps.

Hello Akash,

If you are looking for important questions of class 12th then I would like to suggest you to go with previous year questions of that particular board. You can go with last 5-10 years of PYQs so and after going through all the questions you will have a clear idea about the type and level of questions that are being asked and it will help you to boost your class 12th board preparation.

You can get the Previous Year Questions (PYQs) on the official website of the respective board.

I hope this answer helps you. If you have more queries then feel free to share your questions with us we will be happy to assist you.

Thank you and wishing you all the best for your bright future.

Hello student,

If you are planning to appear again for class 12th board exam with PCMB as a private candidate here is the right information you need:

  • No school admission needed! Register directly with CBSE. (But if you want to attend the school then you can take admission in any private school of your choice but it will be waste of money)
  • You have to appear for the 2025 12th board exams.
  • Registration for class 12th board exam starts around September 2024 (check CBSE website for exact dates).
  • Aim to register before late October to avoid extra fees.
  • Schools might not offer classes for private students, so focus on self-study or coaching.

Remember , these are tentative dates based on last year. Keep an eye on the CBSE website ( https://www.cbse.gov.in/ ) for the accurate and official announcement.

I hope this answer helps you. If you have more queries then feel free to share your questions with us, we will be happy to help you.

Good luck with your studies!

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2.45×10−3 kg

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2,000 \; J - 5,000\; J

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K/2\,

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Option 1)

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Option 2)

6L\, HCl_{(aq)}  is consumed for ever 3L\, H_{2(g)}      produced

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67.2\, L\, H_{2(g)} at STP is produced for every mole Al that reacts .

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0.02

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3.125 × 10-2

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2.5 × 10-2

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Option 1)

decrease twice

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increase two fold

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remain unchanged

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be a function of the molecular mass of the substance.

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twice that in 60 g carbon

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6.023 × 1022

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558.5 × 6.023 × 1023

A pulley of radius 2 m is rotated about its axis by a force F = (20t - 5t2) newton (where t is measured in seconds) applied tangentially. If the moment of inertia of the pulley about its axis of rotation is 10 kg m2 , the number of rotations made by the pulley before its direction of motion if reversed, is

Option 1)

less than 3

Option 2)

more than 3 but less than 6

Option 3)

more than 6 but less than 9

Option 4)

more than 9

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