MathDB
Isosceles triangle and tangent circles

Source: All-Russian Olympiad 2006 finals, problem 10.4

May 7, 2006
geometrygeometric transformationreflectioncircumcirclehomothetysymmetryratio

Problem Statement

Consider an isosceles triangle ABCABC with AB=ACAB=AC, and a circle ω\omega which is tangent to the sides ABAB and ACAC of this triangle and intersects the side BCBC at the points KK and LL. The segment AKAK intersects the circle ω\omega at a point MM (apart from KK). Let PP and QQ be the reflections of the point KK in the points BB and CC, respectively. Show that the circumcircle of triangle PMQPMQ is tangent to the circle ω\omega.