Stage: 5 Challenge Level: 
Can you spot your old friend the 30-60-90 triangle? Then you are
into scaling down and geometric series.
Scale factors. Calculus generally. Inscribed circle. Infinite series. Weekly Challenge. Visualising. Enlargements. Stage 5 - Core Mapping. Maths in STEM. Geometric sequence.
Published April 1999,November 2008,December 2008.
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