Maybe you can try with the t-formulas, let
We are given:
Let's rewrite the integrand:
Now we may state:
That was MarkFL's answer...
Almost simultaneously, galactus wrote:
Notice now we have the form
Since , then (this just comes from looking at a right triangle).
Put all together:
The left most integral is an arctan. The right one is of the form
So, we get after resubbing: