Problem

Source: 2021 Saudi Arabia Training Lists p21 https://artofproblemsolving.com/community/c2758131_2021_saudi_arabia_training_tests

Tags: cyclic quadrilateral, geometry, tangent



Let $ABCD$ be a cyclic quadrilateral with $O$ is circumcenter and $AC$ meets $BD$ at $I$ Suppose that rays $DA,CD$ meet at $E$ and rays $BA,CD$ meet at $F$. The Gauss line of $ABCD$ meets $AB,BC,CD,DA$ at points $M,N,P,Q$ respectively. Prove that the circle of diameter $OI$ is tangent to two circles $(ENQ), (FMP)$