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MathNet 2026 — Part 08 Question 161

Math Olympiad Vault · MathNet 2026 — Part 08

Question 161

In triangle $ABC$, $\angle A = 60^\circ$. Let $E$ and $F$ be points on the extensions of $AB$ and $AC$ such that $BE = CF = BC$. The circumcircle of $ACE$ intersects $EF$ in $K$ (different from $E$). Prove that $K$ lies on the bisector of $\angle BAC$.