Stage: 4 Challenge Level: 
The shape shown is of an equilateral triangle sitting on top of a square.
What is the radius of the circle that circumscribes this shape?
Mathematical reasoning & proof. Congruence. Stage 5 - Reviewed 2012. Symmetry. Inequality/inequalities. Dynamical systems. Manipulating algebraic expressions/formulae. Number theory. Circle theorems. Inscribed polygons.
Published February 2000.
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