Areas of polygons - by an algorithm

This PowerPoint resource is suitable as enrichment in KS3 or in KS4 maths.

It demonstrates the shoelace algorithm, a favourite of the mathematician Gauss, for finding the area of any polygon. The algorithm involves listing the coordinates of the vertices of the polygon and the multiplication, addition and subtraction of integers.

There is a lovely proof of Pythagoras' theorem for KS4 and it provides a hidden link to matrices and their determinants.