Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Indefinite Integration

Question:

$\int cosec^6 x d x$ is equal to

Options:

$-\cot x \frac{\cot ^5 x}{5}-\frac{2 \cot ^5 x}{3}+k$

$-\frac{\cot x}{3}+\frac{2 \cot ^5 x}{5}+2 \cot ^{-3} x+k$

$\frac{\tan ^3 x}{3}-\frac{\tan x}{5}+2 \tan ^3 x+k$

none of these

Correct Answer:

$-\cot x \frac{\cot ^5 x}{5}-\frac{2 \cot ^5 x}{3}+k$

Explanation:

Let $I=\int cosec^6 x d x=\int cosec^4 x . cosec^2 x d x$

$=\int\left(1+\cot ^2 x\right)^2 . cosec^2 x d x=\int\left(1+\cot ^4 x+2 \cot ^2 x\right) . cosec^2 x d x$

∴  $I=-\cot x-\frac{\cot ^5 x}{5}-\frac{2}{3} \cot ^3 x+c$

Hence (1) is the correct answer.