### Proposition

The figure below shows
points A and B on a circle of center O. Circle of center A and radius AB
cuts circle O at C. Circle of center B and radius BA cuts circle O at D.
BO extended cuts circle A at E. Prove that the points C, D, and E are
collinear.

### Poster of Geometry Problem 1404: Sketching, Typography using iPad Apps

See also:
Art of problem 1404, Circle Patterns using Mobile Apps.