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MEMO 2010, Problem T-5: Parallel lines

Source:

September 12, 2010
geometrytrigonometryincentermemo

Problem Statement

The incircle of the triangle ABCABC touches the sides BCBC, CACA, and ABAB in the points DD, EE and FF, respectively. Let KK be the point symmetric to DD with respect to the incenter. The lines DEDE and FKFK intersect at SS. Prove that ASAS is parallel to BCBC.
(4th Middle European Mathematical Olympiad, Team Competition, Problem 5)