MathDB

Geometry with circles

Source: St Petersburg Olympiad 2009, Grade 11, P5

August 30, 2017

geometrycircumcircle

Problem Statement

O

-circumcenter of

ABCD

.

AC

and

BD

intersect in

E

,

AD

and

BC

in

F

.

X,Y

- midpoints of

AD

and

BC

.

O_1

-circumcenter of

EXY

. Prove that

OF \parallel O_1E

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