Hey guys, I'm having trouble solving this definite integral. I'm doing work with polar equations and I was led to this: http://img404.imageshack.us/img404/6021/first4hv.gif [Broken] which I simplified to http://img404.imageshack.us/img404/669/second8qs.gif [Broken] And, using the trig identity cos(x)^2 = (1 + cos(2x))/2, I got this http://img404.imageshack.us/img404/4734/third1jh.gif [Broken] Which then simplifies down to 0. But that is the wrong answer. I know for a fact that the answer is 8. Even Mathematica says the answer is 8. I'm pretty sure my problem lies in the step where I removed the square root, but I don't see what exactly I did wrong. Why is it wrong, and what can I do to evaluate this integral correctly? Thankyou to anyone who helps.