1. The problem statement, all variables and given/known data Use 2 or more substitutions to find the following integrals hint : begin with u=cosx 2. Relevant equations Integral 0--->pi/2 (cosxsinx)/swrt(cos2x+49 dx 3. The attempt at a solution I'm still a little fuzzy on using multiple substitutions. From what I've read on the text and previous easier equations, it just means that there are multiple u=(something) that can work. Is that right? so I tried u=cosx du=-sinxdx giving me -1 * Integral 0--->pi/2 u/sqrt(u2+49) du it's here that I am brickwalling. I really want to know how it works, so if you wouldn't mind a step by step process, I'd appreciate greatly.