Skip to content / Đến nội dung
ThichHocToan.com

MathNet 2011 Question 8

Math Olympiad Vault · MathNet 2011

Question 8

Let $ABC$ be a triangle such that $AB \lt AC$. The perpendicular bisector of the side $BC$ meets the side $AC$ at the point $D$, and the (interior) bisectrix of the angle $ADB$ meets the circumcircle $ABC$ at the point $E$. Prove that the (interior) bisectrix of the angle $AEB$ and the line through the incentres of the triangles $ADE$ and $BDE$ are perpendicular.

Question illustration