IMO 2021 Shortlist G1
Let ABCD be a parallelogram such that AC “ BC. A point P is chosen on the extension of the segment AB beyond B. The circ...
Category: Geometry
Problem
Let ABCD be a parallelogram such that AC “ BC. A point P is chosen on the extension of the segment AB beyond B. The circumcircle of the triangle ACD meets the segment PD again at Q, and the circumcircle of the triangle APQ meets the segment PC again at R. Prove that the lines CD, AQ, and BR are concurrent.