Stage: 4 Challenge Level: 
A square of area 40 cm$^2$ is inscribed in a semicircle.
Find the area of the square that could be inscribed in a circle of the same radius.
Long problems. smartphone. Circles. Stage 5 needs dealing with. Squares. Inscribed polygons. Investigations. Area. Similarity. Pythagoras' theorem.
Published September 2003.
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