MathDB
Prove that two angles are equal in an isosceles triangle

Source: XVII Sharygin Correspondence Round P8

March 2, 2021
geometry

Problem Statement

Let ABCABC be an isosceles triangle (AB=BCAB=BC) and \ell be a ray from BB. Points PP and QQ of \ell lie inside the triangle in such a way that BAP=QCA\angle BAP=\angle QCA. Prove that PAQ=PCQ\angle PAQ=\angle PCQ.