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Isotomic conjugates [intersections of median & incircle]

Source: belgian IMO preparation; IMO Shortlist 2005 geometry problem G6

March 25, 2006
geometryhomothetyreflectiontrapezoidIMO Shortlistprojective geometryPolars

Problem Statement

Let ABCABC be a triangle, and MM the midpoint of its side BCBC. Let γ\gamma be the incircle of triangle ABCABC. The median AMAM of triangle ABCABC intersects the incircle γ\gamma at two points KK and LL. Let the lines passing through KK and LL, parallel to BCBC, intersect the incircle γ\gamma again in two points XX and YY. Let the lines AXAX and AYAY intersect BCBC again at the points PP and QQ. Prove that BP=CQBP = CQ.