Browse by Stream
QnA
Home
QnA
Go To Your Study Dashboard

Get Answers to all your Questions

header-bg qa
  • Home
  • School
  • Please Solve R.D.Sharma Class 12 Chapter 18 Indefinite Integrals Exercise 18.25 Question 50 Maths Textbook Solution.

Please Solve R.D.Sharma Class 12 Chapter 18 Indefinite Integrals Exercise 18.25 Question 50  Maths Textbook Solution.

Answers (1)

Answer: \frac{\sin 3x}{18}-\frac{x\cos 3x}{6}+\frac{x\cos x}{2}-\frac{\sin x}{2}+c

Hint: \int sin\: xdx=\cos \: x&\int \cos \: xdx=-\sin \: x

Given: \int\: x \sin x\cos 2xdx

Solution:

            I=\int\: x \sin x\cos 2xdx

            I=\frac{1}{2}\int\: 2x \sin x\cos 2xdx

            =\frac{1}{2}\int\: x2 \sin x\cos 2xdx

            \begin{aligned} &=\frac{1}{2} \int x[\sin (x+2 x)+\sin (x-2 x)] d x \\ &=\frac{1}{2} \int x \sin 3 x d x-\frac{1}{2} \int x \sin x d x \\ &=\frac{1}{2}\left[x \frac{\cos 3 x}{3}+\frac{1}{3} \int \cos 3 x d x\right]-\frac{1}{2}\left[x \cos x+\int \cos x d x\right] \\ &I=\frac{1}{2}\left[-x \frac{\cos 3 x}{3}+\frac{\sin 3 x}{9}\right]-\frac{1}{2}[-x \cos x+\sin x] \\ &=\frac{1}{2}\left[\frac{\sin 3 x}{9}-\frac{x \cos 3 x}{3}+x \cos x-\sin x\right]+c \\ &=\frac{\sin 3 x}{18}-\frac{x \cos 3 x}{6}+\frac{x \cos x}{2}-\frac{\sin x}{2}+c \end{aligned}

Posted by

infoexpert21

View full answer

Crack CUET with india's "Best Teachers"

  • HD Video Lectures
  • Unlimited Mock Tests
  • Faculty Support
cuet_ads

Similar Questions

Trending Articles/News

anam-khan

CBSE Class 12 board exams 2025 to have 50% competency-based questions; no change in 10th
anam-khan

CBSE Class 12 board exams 2024 over; expected result date, trends of last 10 years
anam-khan

CBSE Class 12 accountancy board exam analysis 2024 out; paper rated easy, balanced

Latest Question