MathDB

Parallelism

Source: Indian RMO 2000 Problem 5

October 27, 2005

geometrycircumcircleperpendicular bisectorangle bisector

Problem Statement

The internal bisector of angle

A

in a triangle

ABC

with

AC > AB

meets the circumcircle

BE

of the triangle in

D

. Join

D

to the center

O

of the circle

\Gamma

and suppose that

DO

meets

AC

in

E

, possibly when extended. Given that

BE

is perpendicular to

AD

, show that

AO

is parallel to

BD

.

Back to Problems View on AoPS