Problem

Source: IMO Shortlist 2023 G5

Tags: geometry, IMO Shortlist, AZE IMO TST



Let ABC be an acute-angled triangle with circumcircle ω and circumcentre O. Points DB and EC lie on ω such that BDAC and CEAB. Let CO meet AB at X, and BO meet AC at Y. Prove that the circumcircles of triangles BXD and CYE have an intersection lie on line AO. Ivan Chan Kai Chin, Malaysia