K is the orthocenter of II_aE, excenter (Kharkiv City X 2019 Ukr)
Source:
March 22, 2020
geometryexcenterincenterangle bisectormidpointKharkiv
Problem Statement
In triangle , point is incenter , is the -excenter. Let be the intersection point of the with the external bisector of the angle , and be the midpoint of the arc of the circumcircle of triangle . Prove that is the orthocenter of triangle .