MathDB
Similar triangles and equal segments

Source: BMO SL 2023 G2

May 3, 2024
geometryBMO Shortlist

Problem Statement

Let ABCDABCD be a cyclic quadrilateral with circumcenter OO lying in the interior. Let EE and FF be the midpoints of the segments BCBC and ADAD, respectively. Let XX be the point lying on the same side of the line EFEF as the vertex CC such that EXF\triangle EXF and BOA\triangle BOA are similar. Prove that XC=XDXC = XD.