MathDB

2

Part of 2008 Finnish National High School Mathematics Competition

Problems(1)

Perpendicular segments

Source: Finnish Mathematics Competition 2008, Final Round, Problem 2

11/14/2011
The incentre of the triangle ABCABC is I.I. The lines AI,BIAI, BI and CICI meet the circumcircle of the triangle ABCABC also at points D,ED, E and F,F, respectively. Prove that ADAD and EFEF are perpendicular.
geometryincentercircumcirclepower of a pointradical axis