I would say the easiest way to do it is to just graph and find the distance from one side of the circle to the origin.
The distance from the left end of the circle to the center is 8.
Applying this to the circle area formula:
A=pi*r^{2}
A=pi*8^{2}
You can calculate the rest by yourself by entering pi*8^{2} in a calc.
-Vinculum