MathDB

TOT 2006 Fall - Senior O-Level p2 lines joining incenters perpendicular

Source:

February 25, 2020

geometryincenterperpendicular

Problem Statement

The incircle of the quadrilateral

ABCD

touches

AB,BC, CD

and

DA

E, F,G

and

H

respectively. Prove that the line joining the incentres of triangles

HAE

and

FCG

is perpendicular to the line joining the incentres of triangles

EBF

and

GDH

. (4)