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tangent circumcircles

Source: 2019 Oral Moscow Geometry Olympiad grades 8-9 p4

May 21, 2019
geometryperpendicular bisectortangent circlescircumcircle

Problem Statement

The perpendicular bisector of the bisector BLBL of the triangle ABCABC intersects the bisectors of its external angles AA and CC at points PP and QQ, respectively. Prove that the circle circumscribed around the triangle PBQPBQ is tangent to the circle circumscribed around the triangle ABCABC.