1. ## Integration

I have to integrate $2dx/sin(x)^2$.

The calculator gave me the answer of $-2/tan(x)$, but I'm not sure how to get there.

2. Which the derivative of cotan(x) ?

3. Yes. How do you integrate sin(x)^2 into tan(x)? Do you have to substitute something?

4. note that $\frac{2}{\sin^2{x}} = 2\csc^2{x}$

5. Originally Posted by skeeter
note that $\frac{2}{\sin^2{x}} = 2\csc^2{x}$
But how does that turn into 2/tan(x)? wouldn't it just be 2tan(x)?

6. Originally Posted by Nacho
Which the derivative of cotan(x) ?
$
\left( {\cot x} \right)^\prime = - \csc ^2 x \Rightarrow \cot x = - \int {\csc ^2 xdx} \Leftrightarrow \frac{2}
{{\tan x}} = - \int {\frac{2}
{{\sin ^2 x}}dx}
$

7. Okay. I get it now. There are two substitutions. Once to get csc from sin and another time to get tan from cot.

Thank you.