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Parallel lines involving the A-excenter

Source: Germany 2016 - Problem 3

June 19, 2016
geometrycircumcircleexcenterparallelorthocenter

Problem Statement

Let IaI_a be the AA-excenter of a scalene triangle ABCABC. And let MM be the point symmetric to IaI_a about line BCBC. Prove that line AMAM is parallel to the line through the circumcenter and the orthocenter of triangle IaCBI_aCB.
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