How to integrate $\frac{x^2}{1-x^2}$ I want to integrate 
\[\frac{x^2}{1-x^2},\]
what I have try is trigonometric substitution and partition function and integration by part 
but still cannot solve it
Thx for your reading!

And going a little further,
$$\frac{1}{x^2-1} = \frac{1}{(x-1)(x+1)}
=\frac{1}{2}\left(\frac{1}{x-1}-\frac{1}{x+1}\right)
$$
At this point, even I can integrate it.
