Let A, B, C be points on circle O such that AB is a diameter, and CO is perpendicular to AB. Let P be a point on OA, and let line CP intersect the circle again at Q. If OP = 20 and PQ = 8, find r^2, where r is the radius of the circle.
https://web2.0calc.com/questions/let-a-b-c-be-points-on-circle-o-such-that-ab-is-a-diameter#r2
