MathDB
Seem like some well-known lemma

Source: Kürchák 2018 P1

October 8, 2018
geometry

Problem Statement

Given a triangle ABCABC with its incircle touching sides BC,CA,ABBC,CA,AB at A1,B1,C1A_1,B_1,C_1, respectively. Let the median from AA intersects B1C1B_1C_1 at MM. Show that A1M⊥BCA_1M\perp BC.
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