Iran geometry
Source: Iranian TST 2020, second exam day 1, problem 3
March 11, 2020
geometrycircumcircleincenterIranian TST
Problem Statement
Given a triangle with circumcircle . Points and are the foot of angle bisectors of and , is incenter and is the intersection of and . Suppose that be the midpoint of arc . Circle intersects the -median and circumcircle of for the second time at and . Let be the reflection of across and be the second intersection of circumcircle of and . Prove that quadrilateral is cyclic. Proposed by Alireza Dadgarnia and Amir Parsa Hosseini