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MathNet 2018-part-05 — 181 problems (EN–VI) Question 67

Math Olympiad Vault · MathNet 2018-part-05 — 181 problems (EN–VI)

Question 67

Let $ABC$ be an acute-angled triangle inscribed in circle $(O)$. Let $G$ be a point on the small arc $AC$ of $(O)$ and $(K)$ be a circle passing through $A$ and $G$. The bisector of $\angle BAC$ cuts $(K)$ again at $P$. The point $E$ is chosen on $(K)$ such that $AE$ is parallel to $BC$. The line $PK$ meets the perpendicular bisector of $BC$ at $F$. Prove that $\angle EGF = 90^{\circ}$.