Skip to content / Đến nội dung
ThichHocToan.com

MathNet 2026 — Part 04 Question 113

Math Olympiad Vault · MathNet 2026 — Part 04

Question 113

Let $ABC$ be a triangle with $\widehat{BAC}=60^{\circ}$. Let $D$ and $E$ be the feet of the bisectors from the vertices $B$ and $C$ respectively. Let $I$ be the intersection point of the line $(BD)$ and $(CE)$. Show that points $A$, $I$, $D$ and $E$ are cocyclic.