solve:

$\displaystyle \int \frac{dx}{x^2 (\sqrt{x^2+1})}$

I use these trig subs:

$\displaystyle x=tan\theta$

$\displaystyle dx=sec^2 \theta \\d\theta$

after substituting and simplifying I end up here:

$\displaystyle \int \frac{sec\theta}{tan^2\theta} \\d\theta$

Any help in getting "unstuck" would be appreciated!