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KöMaL 2011 A540

    Let A1A2A3A_1 A_2 A_3 be a non-equilateral triangle, let point MM be its orthocenter, let FF be its Feuerbach point, and let kk be the circumcircle of the triangle. For ii=1,2,3 denote by kik_i the circle that is internally tangent to kk and tangent to the sides AiAi+1A_i A_{i+1} and AiAi+2A_i A_{i+2}. (The indices are considered modulo 3, i.e. A4A_4=A1A_1 and A5A_5=A2A_2.) Let TiT_i be the point of tangency between kk and kik_i. Prove that the lines A1T1A_1 T_1, A2T2A_2 T_2, A3T3A_3 T_3 and MFMF are concurrent.

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