Problem

Source: LMAO 2024 P4

Tags: geometry, lmao, LMAO Mock



Let $ABC$ be a triangle with circumcenter $O$ and $\angle BAC = 60^{\circ}$. The internal angle bisector of $\angle BAC$ meets line $BC$ and the circumcircle of $\triangle ABC$ in points $M,L$ respectively. Let $K$ denote the reflection of $BL\cap AC$ over the line $BC$. Let $D$ be on the line $CO$ with $DM$ perpendicular to $KL$. Prove that points $K,A,D$ are collinear. Proposed by Sanjana Philo Chacko