1. The problem statement, all variables and given/known data http://i50.tinypic.com/zxw6qr.png a>0 a ∫ x√(x^2+a^2)dx (a>0) 0 2. The attempt at a solution u=x^2+a^2 du=2xdx I looked it up online and I saw you needed to use trig. How do you use trig for this problem? Note: I have not learned integration by parts, just u-sub.