Stage: 5 Challenge Level: 
Area fomulas and a little trig will help.
Here is the diagram if you need some clues to get started:
Symmetry. Summation of series. Area. Arcs, sectors and segments. Geometric mean. Manipulating algebraic expressions/formulae. Mathematical reasoning & proof. epsilons. alphas. Stage 5 - Reviewed 2012.
Published March 1999.
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