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PrintIMO Team Selection Contest I
Estonia geometry
Problem
Let be a triangle with and let be its incenter. The line meets at , and the line through perpendicular to meets at . Prove that the reflection of in lies on the circumcircle of triangle .
Solution
Solution. See IMO 2016 shortlist, problem G4.
Techniques
Triangle centers: centroid, incenter, circumcenter, orthocenter, Euler line, nine-point circleCyclic quadrilateralsAngle chasing