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MathNet 2020 — Math Olympiad Vault — Part 01 Question 1

Math Olympiad Vault · MathNet 2020 — Math Olympiad Vault — Part 01

Question 1

Let $\Gamma$ be the circumcircle of $\triangle A B C$. Let $D$ be a point on the side $B C$. The tangent to $\Gamma$ at $A$ intersects the parallel line to $B A$ through $D$ at point $E$. The segment $C E$ intersects $\Gamma$ again at $F$. Suppose $B, D, F, E$ are concyclic. Prove that $A C, B F, D E$ are concurrent.