Math: Geometry Problem 1003:
Intersecting Circle, Circumcircle, Chord, Secant, Triangle,
90 Degree, Angle, Perpendicular Lines. Level: School, College.
The figure below shows circles O and Q
intersecting at A and B. Chord CB extended meets circle O at C,
chord CA extended meets circle O at E. Circumcircle of triangle CDE
intersects circle Q at F. Prove that the measure of angle OFC is