Geometry · Isosceles triangles · Angle bisectors · Incentre · Parallelograms · Midpoints
Problem 5, 2019
Let \(ABC\) be a triangle. Points \(D\) and \(E\) lie on the rays \(CA\) and \(CB\) respectively, but not on the sides of the triangle \(ABC\), and are chosen so that
\[ |AD| = |BE| = |AB| . \]
Let \(G\) be the point where the lines \(AE\) and \(BD\) meet, and let \(I\) be the centre of the circle inscribed in the triangle \(ABC\). Prove that the line \(GI\) passes through the midpoint of the side \(AB\).
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Slovenian High School Mathematics Competition for Vega Awards (MaSSA), drzavno (national) round 2019, 1. letnik, category A, problem B2. Organized by DMFA Slovenije (Society of Mathematicians, Physicists and Astronomers of Slovenia). Source