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Need Solution for R.D.Sharma Maths Class 12 Chapter 18 Indefinite Integrals Exercise Revision Exercise Question 80 Maths Textbook Solution.

Answers (1)

Answer:

I=\frac{\tan ^{5} x}{5}+\frac{2 \tan ^{8} x}{3}+\tan x+c

Hint:

To solve the given equation we have to split sec? x into sec? x sec² x.

Given:

\int \sec ^{6} x d x

Solution:

I=\int \sec ^{6} x d x

    =\int \sec ^{4} x \sec ^{2} x d x

    =\int\left(\sec ^{2} x\right)^{2} \sec ^{2} x d x

  \sec ^{2} x=\tan ^{2} x+1

 I=\int\left(\tan ^{2} x+1\right)^{2} \sec ^{2} x d x

 \left[\because \tan x=t \quad, \sec ^{2} x d x=d t\right.

I=\int\left(t^{2}+1\right)^{2} d t

I=\int\left(t^{4}+2 t^{2}+1\right) d t

I=\frac{t^{5}}{5}+\frac{2 t^{3}}{3}+t+c

I=\frac{\tan ^{5} x}{5}+\frac{2 \tan ^{3} x}{3}+\tan x+c

 

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