Write a value

Question:

Write a value of $\int \frac{\sin \mathrm{x}}{\cos ^{3} \mathrm{x}} \mathrm{dx}$

Solution:

Let, $\cos x=t$

Differentiating both sides with respect to $\mathrm{x}$

$\frac{d t}{d x}=-\sin x$

$\Rightarrow-d t=\sin x d x$

$y=\int \frac{-1}{t^{3}} d t$

Use formula $\int \frac{1}{t^{n}} d t=\frac{t^{-n+1}}{-n+1}$

$y=-\frac{t^{-2}}{-2}+c$

Again, put $t=\cos x$

$y=\frac{1}{2(\cos x)^{2}}+c$

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