MathDB
2019 Serbia MO Day 1 P3

Source: 2019 Serbia MO

April 7, 2019
geometry

Problem Statement

Let kk be the circle inscribed in convex quadrilateral ABCDABCD. Lines ADAD and BCBC meet at PP ,and circumcircles of PAB\triangle PAB and PCD\triangle PCD meet in XX . Prove that tangents from XX to kk form equal angles with lines AXAX and CXCX .