Fig. 330—Double compound triangle
[Figure 329] shows a design in which the extended triangles are even more regular and simple, with triangular terraced figures on their inner edge. The median figure is a triangle instead of a rectangle.
Fig. 331—Double rectangle; median rectangle
[Figure 330] shows the same design with modification in the position of the median figure, and a slight curvature in two of its sides.
Fig. 332—Double rectangle; median triangle