Skip to content / Đến nội dung
ThichHocToan.com

MathNet 2010 — Part 04 Question 3

Math Olympiad Vault · MathNet 2010 — Part 04

Question 3

Let $A, B, C, D, E$ be points such that $A B C D$ is a cyclic quadrilateral and $A B D E$ is a parallelogram. The diagonals $A C$ and $B D$ intersect at $S$ and the rays $A B$ and $D C$ intersect at $F$. Prove that $\angle A F S=\angle E C D$.