I'm still learning this myself, but I'm fairly sure that you would do this using substitution. I'm not suggesting that this is the best way to solve it, but note how using alters the question:
Perhaps you'll be able to solve it from here?
I suggest you combine the terms and then take as a common factor and take it out. Then use a substitution that will get rid of the outside, and use another (trigonometric) substitution to solve. This way isn't pretty and I'm trying to find another easier way.
EDIT: @Jhevon: he did pepper it with parentheses, so I don't think there is an ambiguity here: the is in the square root.
EDIT2: See ya!