Stage: 3 Challenge Level: 
The radius of the circle is $1$ unit long.
You can use the radius as the hypotenuse of the right-angled triangles.
Area. Circles. Pythagorean triples. Cosine. smartphone. Squares. Mathematical reasoning & proof. Visualising. Sine. Pythagoras' theorem.
Published June 2007.
Copyright © 2007. University of Cambridge. All rights reserved.
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