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Angle to Chord

Weekly Problem 23 - 2008
A triangle has been drawn inside this circle. Can you find the length of the chord it forms?


Stage: 4 Challenge Level: Challenge Level:2 Challenge Level:2

Two intersecting circles have a common chord AB. The point C moves on the circumference of the circle C1. The straight lines CA and CB are extended to meet the circle C2 at E and F respectively.

As the point C moves what do you notice about the chord EF?

Give a proof of your conjecture.


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