Skip to content / Đến nội dung
ThichHocToan.com

VN TST 2006 Question 1

VMO · VN TST 2006

Question 1

Let $ABC$ be a triangle with orthocenter $H$. The external bisector of $\angle BHC$ meets sides $AB$ and $AC$ at $D$ and $E$, respectively. The internal bisector of $\angle BAC$ meets the circumcircle of triangle $ADE$ at $K$. Prove that line $HK$ passes through the midpoint of $BC$.