So I've had a problem on my mind for most of today, and although I'm sure the answer is quite simple, I can't seem to figure out how to go about doing this.

The question is this: Suppose you had two circles (A and B) of equal size with a radius $\displaystyle x$. If the two circles were arranged such that the circumference of each circle passed through the center of the other, what would be an expression in terms of $\displaystyle x$ for the area where the two circles overlap?

Diagram of what I'm talking about is below (A and B are the centers of the circles):

The area I'm looking for being the middle section.

Hints on how to go about finding it, or a direct solution would be much appreciated :V