Stage: 5 Challenge Level: 
You may wish to try the problem Bendy Quad first.
Four rods are hinged at their ends to form a quadrilateral with fixed side lengths.
Show that the quadrilateral has a maximum area when it is cyclic.
Maximise/minimise/optimise. Stage 5 - Reviewed 2012. Summation of series. Quadrilaterals. Mathematical reasoning & proof. alphas. epsilons. Cosine rule. Manipulating algebraic expressions/formulae. Area formulae. Inequality/inequalities.
Published June 2000.
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