Given a triangle ABC (see the dynamic figure
below), Medians AA1, BB1, and CC1, meet the circumcircle O at A2, B2, and C2, respectively. Tangents at A, B, and C form a triangle A3B3C3. Prove that (1) Lines A3A2, B3B2, and C3C2
are concurrent at a point E, called the Exeter point. (2) E lies on the
Exeter Point Puzzle.
Kimberling, Clark. "Encyclopedia
of Triangle Centers: X(22)"
Dynamic Geometry Environment (DGE) or Interactive Geometry Software
(IGS) of the Exeter Point
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Static Diagram of Exeter Point