Stage: 3 and 4 Challenge Level: 
The problem Triangles in Circles will help if you are having difficulty calculating angles.
Try an even number of points round the edge.
Proving this will be easier if you join all the points to the centre and look for isosceles triangles.
Try an even number of points round the edge.
Proving this will be easier if you join all the points to the centre and look for isosceles triangles.
Pinboard/geoboard. Rotations. Right angled triangles. Interactivities. Making and proving conjectures. Circle theorems. Mathematical reasoning & proof. Games. Complex numbers. Dynamic geometry.
Published July 2005,August 2005.
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