The n – 2 triangles can be regarded as “footprints” left by
the triangular pieces obtained by dissecting the original poly-
gon with n – 3 diagonals from a given vertex to each of the
nonadjacent vertices, as illustrated in Figure 5 for n = 6.
The sum of the areas of these triangles is equal to the area of
the region enclosed by the regular polygon. This is illus-
trated for the regular hexagon in Figure 6.