The circles O and O_{1} intersect at A and B (see the figure above),
CD is the common external tangent, CA intersects circle O_{1} at E,
DA intersects circle O at F, FC and
ED intersect at G, BA intersects CD at H. If O_{2} is the circumcenter of triangle CGD, prove that
the points G, O_{2}, and H are collinear.
Dynamic Geometry of Problem 898
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