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.
8⋅√202+r2=(r−20)(r+20)
64⋅400+49r2=r4−800r2+4002=0
r2=(√849+√1832012)2
r2=approx.638.5,r=approx.25.3
