Question

Evaluate the following double integral:

Answer 1

The answer is listed. I'm just not sure how to integrate it. Trig sub? To reduce a double integral to a single integral, integrate by one variable while holding the other variable constant and evaluate resulting expression at the appropriate bounds. My problem is the simple integration.

Answer 2

Integrate by one variable while holding the other constant

Answer 3

also a u-sub

Answer 4

that's what I'm having trouble with. I'm not sure how to start the u sub.