Write a program that lets the user define a circle by clicking three points.

Hint: The key to solving this problem is to find a circle that passes through the users' three points. There are several approaches that you can take, but the one I use is to note that the perpendicular bisectors of a chord of a circle always pass through the circle's center.

The following diagram shows three points on a circle A, B, and C. The dashed lines show perpendicular bisectors for the segments AB and BC. The point where the bisectors intersect is the circle's center: