The center going through (-9,2) gives you A and B (x - - 9)^2 + (y - 2)^2 = r^2 (x + 9)^2 + (y - 2)^2 = r^2
Going from the center to the given point gives you the radius. We need the r^2 which is the way the distance formula works: it will give you r^2. c = r^2
The shared angle, the marked angle, and the marked sides between those angles are congruent. That is, you have congruent Angle, Side, Angle, so the ASA postulate applies.
