Pentagon divided into three triangles
A pentagon triangulated (f, e, g, d, c) with two further pentagons broken into parts
A pencil sheet on the triangulation of polygons. A pentagon is divided into three triangles with its points labelled f, e, g, d and c, and a short segment a b is drawn alongside; two further pentagons are set out with their parts separated. Together they study how a polygon can be decomposed into its constituent triangles. The page carries the old number 19.
On this page
Pentagon split into three triangles (f, e, g, d, c)
A pentagon is divided into three triangles, its points marked f, e, g, d and c. The construction shows how a five-sided figure is reduced to triangles in order to measure its area.
Two further pentagons broken into their parts
Two more pentagons are drawn with their component parts separated out beside them, continuing the decomposition of polygons into triangles. A short reference segment a b accompanies the figures.