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Midpoints of chords of an excircle through the circumcircle

Source: XVIII Tuymaada Mathematical Olympiad (2011), Junior Level

July 29, 2011
geometrycircumcirclegeometry unsolved

Problem Statement

An excircle of triangle ABCABC touches the side ABAB at PP and the extensions of sides ACAC and BCBC at QQ and RR, respectively. Prove that if the midpoint of PQPQ lies on the circumcircle of ABCABC, then the midpoint of PRPR also lies on that circumcircle.