Problem

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

Tags: geometry, perpendicular bisector, tangent circles, circumcircle



The perpendicular bisector of the bisector $BL$ of the triangle $ABC$ intersects the bisectors of its external angles $A$ and $C$ at points $P$ and $Q$, respectively. Prove that the circle circumscribed around the triangle $PBQ$ is tangent to the circle circumscribed around the triangle $ABC$.