Problem

Source: JBMO Shortlist 2023, G3

Tags: JBMO, JBMO Shortlist, geometry, circumcircle, tangent circles



Let $A,B,C,D$ and $E$ be five points lying in this order on a circle, such that $AD=BC$. The lines $AD$ and $BC$ meet at a point $F$. The circumcircles of the triangles $CEF$ and $ABF$ meet again at the point $P$. Prove that the circumcircles of triangles $BDF$ and $BEP$ are tangent to each other.