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## Homework Statement

Use 2 or more substitutions to find the following integrals

hint : begin with u=cosx

## Homework Equations

Integral 0--->pi/2 (cosxsinx)/swrt(cos

^{2}x+49 dx

## 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(u

^{2}+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.