Stage: 4 Challenge Level: 
Possible extension
Try the problem Giant Holly Leaf. It does not require any more mathematical knowledge than this problem but it introduces the concept of curvature.
See also the article Curvature of Surfaces.
Long problems. Pythagoras' theorem. Symmetry. Arcs, sectors and segments. Circles. Pythagorean triples. Circumferences. Cosine rule. Graph sketching. Stage 5 needs dealing with.
Published December 1999.
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