Skip to content / Đến nội dung
ThichHocToan.com

MathNet 2010 — Part 04 Question 2

Math Olympiad Vault · MathNet 2010 — Part 04

Question 2

The incircle of the triangle $ABC$ touches the sides $BC$, $CA$, and $AB$ in the points $D$, $E$, and $F$, respectively. Let $K$ be the point symmetric to $D$ with respect to the incenter. The lines $DE$ and $FK$ intersect at $S$. Prove that $AS$ is parallel to $BC$.