MathDB
Common point

Source: Polish MO second round 2012

February 19, 2012
geometryincentercircumcirclegeometric transformationreflectiontrigonometryparallelogram

Problem Statement

Let ABCABC be a triangle with ∠A=60∘\angle A=60^{\circ} and AB≠ACAB\neq AC, II-incenter, OO-circumcenter. Prove that perpendicular bisector of AIAI, line OIOI and line BCBC have a common point.
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