Let $ABCD$ be a cyclic quadrilateral and let $k_1$ and $k_2$ be circles inscribed in triangles $ABC$ and $ABD$. Prove that external common tangent of those circles (different from $AB$) is parallel with $CD$
Problem
Source: Regional Olympiad - Federation of Bosnia and Herzegovina 2018
Tags: geometry, cyclic quadrilateral, incircle, tangent, parallel