MathDB

CO _|_ DE wanted, 2 circles related

Source: TOT 454 1995 Spring S O3 - Tournament of Towns

July 9, 2024

perpendiculargeometry

Problem Statement

Triangle

ABC

is inscribed in a circle with center

O

. Let

q

be the circle passing through

A

O

and

B

. The lines

CA

and

CB

intersect

q

at the points

D

and

E

(different from

A

and

B

). Prove that the lines

CO

and

DE

are perpendicular to each other.
(S Markelov)