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MathNet 2018-part-04 — 181 problems (EN–VI) Question 103

Math Olympiad Vault · MathNet 2018-part-04 — 181 problems (EN–VI)

Question 103

Let $ABC$ be an acute triangle with $AB \lt AC$, let $G$ be its centroid and $D$ the foot of the altitude from $A$. The line $DG$ meets the small arc $BC$ of the circumcircle of triangle $ABC$ at point $E$. Prove that the line $AB$ is tangent to the circumcircle of triangle $BDE$.