Interesting Math Problem Whose Answer Eludes Me...(Well, maybe not so interesting but can someone please help me out?)

I have had trouble with this one. What is the answer for x, and how did you find that answer?

x=√(2+√(2+√2)...

basically the square root of the quantity of 2 plus the square root of two plus the quantity of two plus...continues in same form forever. Is there anyone who might know the answer to this or has this one before?