2022 TMO Geometry
Source: 2022 Taiwan Mathematics Olympiad
February 19, 2022
geometry
Problem Statement
Let be the -excenter of an acute triangle . Let , be two points on the circumcircle of the triangle such that . Let be a point lies on such that is tangent to the circumcircle of the triangle . Let be a point lies on the circumcircle of the triangle such that is parallel to .
Prove that .Proposed by Li4.