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China TST 1996 diameter circle cut

Source: China TST 1996, problem 1

May 17, 2005
geometrytrapezoidChina

Problem Statement

Let side BCBC of ABC\bigtriangleup ABC be the diameter of a semicircle which cuts ABAB and ACAC at DD and EE respectively. FF and GG are the feet of the perpendiculars from DD and EE to BCBC respectively. DGDG and EFEF intersect at MM. Prove that AMBCAM \perp BC.