MathDB

2024 Geo Problem 10

Source:

April 15, 2024

geometry

Problem Statement

Let

\Omega

be a unit circle with diameter

AB

and center

O

. Let

C

,

D

be on

\Omega

and lie on the same side of

AB

such that

\angle CAB = 50^\circ

and

\angle DBA = 70^\circ

. Suppose

AD

intersects

BC

at

E

. Let the perpendicular from

O

to

CD

intersect the perpendicular from

E

to

AB

at

F

. Find the length of

OF

.
Proposed by Puhua Cheng

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