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(MNP) cuts triangle ABC and froms equilateral - 2003 Cuba MO 2.3

Source:

September 15, 2024
geometryEquilateral

Problem Statement

Let ABCABC be an acute triangle and TT be a point interior to this triangle. that ATB=BTC=CTA\angle ATB = \angle BTC = \angle CTA. Let M,NM,N and PP be the feet of the perpendiculars from TT to BCBC, CACA and ABAB respectively. Prove that if the circle circumscribed around MNP\vartriangle MNP cuts again the sides BC BC, CACA and ABAB in M1M_1, N1N_1, P1P_1 respectively, then the M1N1P1\vartriangle M_1N_1P_1 It is equilateral.