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collinearity wanted, 2 points inside arc are chosen, perpendiculars related

Source: Tuymaada Junior 2004 p3

May 11, 2019
geometrycollinearperpendiculararc

Problem Statement

Point O O is the center of the circumscribed circle of an acute triangle Abc Abc . A certain circle passes through the points B B and C C and intersects sides AB AB and AC AC of a triangle. On its arc lying inside the triangle, points D D and E E are chosen so that the segments BD BD and CE CE pass through the point O O . Perpendicular DD1 DD_1 to AB AB side and perpendicular EE1 EE_1 to AC AC side intersect at M M . Prove that the points A A , M M and O O lie on the same straight line.