MathDB

1

Part of 2003 Finnish National High School Mathematics Competition

Problems(1)

Perpendicularity

Source: Finnish Mathematics Competition 2003, Final Round, Problem 1

11/14/2011
The incentre of the triangle ABCABC is I.I. The rays AI,BIAI, BI and CICI intersect the circumcircle of the triangle ABCABC at the points D,ED, E and F,F, respectively. Prove that ADAD and EFEF are perpendicular.
geometryincentercircumcirclegeometry unsolved