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H be a point symmetric to B under PT

Source: Vietnam TST 2001 for the 42th IMO, problem 2

June 26, 2005
geometrycircumcircletrigonometrygeometric transformationreflectionpower of a pointradical axis

Problem Statement

In the plane let two circles be given which intersect at two points A,BA, B; Let PTPT be one of the two common tangent line of these circles (P,TP, T are points of tangency). Tangents at PP and TT of the circumcircle of triangle APTAPT meet each other at SS. Let HH be a point symmetric to BB under PTPT. Show that A,S,HA, S, H are collinear.