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A rather famous lemma in geometry

Source: Bundeswettbewerb Mathematik 2022, Round 1 - Problem 3

March 30, 2022
geometrytangentangle bisectorgeometry solvedtangent circlescurvilinear incircles

Problem Statement

A circle kk touches a larger circle KK from inside in a point PP. Let QQ be point on kk different from PP. The line tangent to kk at QQ intersects KK in AA and BB. Show that the line PQPQ bisects APB\angle APB.