Calculating the radius of a circular segment

[mklotz]

The radius calculation here can also be used to find a circle that will pass through three (non-colinear) points.

If you have the three points identified as A, B, and P in the diagram, the calculation will, as described, find the radius of the circle that passes through those points.

Finding the center of that circle is trivial. Using the calculated radius, draw a circle around two of the points. One of the intersection points of those circles is the center of the circle passing through all three points. It should be obvious which it is but, if unsure, draw a circle around the remaining point; where all three circles intersect is the center.