Stage: 4 and 5 Challenge Level: 
Look for symmetry.
Make a conjecture.
To prove it, draw some radii.
Can you see any similar triangles?
Similarity. Coordinates. Reflections. Radius (radii) & diameters. Interactivities. Dynamic geometry. Rotations. Tangents. Isosceles triangles. Scale factors.
Published October 1998,September 2008.
Copyright © 2007. University of Cambridge. All rights reserved.
NRICH is part of the family of activities in the Millennium Mathematics Project, which also includes the Plus and Motivate sites.
email: nrich@damtp.cam.ac.uk