Geometry Question

Can one of you math whiz tell me how to find the center of a circle? The way I've done it is to use a triangle in the circle and find half the length of each side of the triangle. Then draw a line exactly 90 degree at the half way mark of each side of the triangle and where they intersect is the center. Is there an easier way?

Thanks in advance
Dave

Attached Image:

fold your monitor into quarters...Simple!