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Prove QR=RT

Source: Mexican Mathematical Olympiad 2016

November 7, 2016
geometry

Problem Statement

Let C1C_1 and C2C_2 be two circumferences externally tangents at SS such that the radius of C2C_2 is the triple of the radius of C1C_1. Let a line be tangent to C1C_1 at PSP \neq S and to C2C_2 at QSQ \neq S. Let TT be a point on C2C_2 such that QTQT is diameter of C2C_2. Let the angle bisector of SQT\angle SQT meet STST at RR. Prove that QR=RTQR=RT