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MathNet 2026 — Part 06 Question 14

Math Olympiad Vault · MathNet 2026 — Part 06

Question 14

The incentre of triangle $ABC$ is $I$, and $H$ is the foot of the perpendicular from $I$ on $AB$. The perpendicular from $H$ on $BC$ meets $BC$ at $E$, and it meets the bisector of $\angle ABC$ at $D$. The perpendicular from $A$ on $BC$ meets $BC$ at $F$. Prove that $\angle BAC = 2\angle EFD$.