Stage: 3 Challenge Level: 
ABC is an equilateral triangle and P is a point in the interior of the triangle.
We know that AP = 3cm and BP = 4cm.
Prove that CP is less than 7cm.
Cubes. Mixed triangles. Locus/loci in 2D. Creating expressions/formulae. Generalising. Mathematical reasoning & proof. Interactivities. Visualising. Working systematically. Squares.
Published October 1997.
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