Monthly Archives: January 2026

Let $O$ be the circumcenter of $\triangle{ABC}$, and $O$ does not lies on $AB$, $BC$ or $CA$. Let $D$, $E$, and $F$ be circumcenters of $\triangle{OBC}$, $\triangle{OCA}$, and $\triangle{OAB}$, respectively. Let $G$ be the the circumcenter of $\triangle{OEF}$. Prove that … Continue reading →