hidden configuration
Source: Brazilian Mathematical Olympiad 2024, Level 2, Problem 6
October 12, 2024
geometryparallelisoscelesexcirclemidpoint
Problem Statement
Let be an isosceles triangle with . Let be a point on segment , be a point on segment , and be a point on segment such that and . Let be the midpoint of . The line parallel to through intersects at and the line parallel to through intersects at . The lines and intersect at . Prove that is perpendicular to .