Known since Antiquity: The Platonic Solids

We are all familiar with basic shapes from school. Recall, the idea of regular polygons, which are shapes with equal angles and sides of equal length e.g a square, an equilateral triangle, a regular pentagon.

A polygon which is not regular is said to be irregular. For example, a right angled triangle has two angles which are 45 degrees and one with 90 degrees. A rectangle, although has 4 angles of equal value (90 degrees), has sides of different length.