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MathNet 2020 — Math Olympiad Vault — Part 03 Question 142

Math Olympiad Vault · MathNet 2020 — Math Olympiad Vault — Part 03

Question 142

Let a triangle $ABC$ such that $|AC| \lt |AB|$ be given, together with its circumcircle. Let $D$ be a varying point on the short arc $AC$. Let $E$ be the reflection of $A$ in the internal angular bisector of $\angle BDC$. Prove that the line $DE$ passes through a fixed point, independent of where $D$ lies.