Proving the formula for the surface area of a sphere

Okay. (I've not posted on here before so forgive me if I'm not typing things properly or whatever).

In one of my assignment questions (I'm a 1st year Maths degree student, by the way) I have to prove the formula for the surface area of a sphere using the surface of revolution formula. So basically, my answer should be 4*Pi*r². I'm having difficulty with it, though. So far within the integral I have this horrible looking thing...

http://i198.photobucket.com/albums/a...leintegral.jpg

(I thought posting a picture would be easier than trying to type it all out). Those should be x²s on the ends of the fraction by the way - the bracket kinda cuts that off. That has to simplify a little, otherwise, I've done something wrong in my calculations prior to arriving at that.

Any ideas?

Cheers.