Let AHA, BHB, CHC be the altitudes of a triangle ABC. The extensions of AHA, BHB, CHC intersect the circumcircle O at A1, B1, C1. Prove that (1) HAHB // A1B1, similarly HBHC // B1C1, HAHC // A1C1; (2) Area A1, B1C1.
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Ten problems: 1411-1420
Similarity, Ratios, Proportions
HTML5 and Dynamic Geometry
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