Dipyramid

A dipyramid, also called a bipyramid, consists of two pyramids symmetrically placed base-to-base. The dipyramids are duals of the regular prisms. Their skeletons are the dipyramidal graphs.

The volume of a dipyramid of half-height and base area is equal to twice the volume of the corresponding pyramid, namely

(1)

The volume of a dipyramid whose base is a regular -sided polygon with side is therefore

(2)

The canonical dipyramids are the duals of the right regular equilateral prisms and if the original prism has edge length , the midradius of the dual dipyramid is

(3)

An octagonal dipyramid is the convex hull of the second octahedron 2-compound.

The angles of the isocelese triangular faces in a canonical -dipyramid as illustrated above are given by

			(4)
			(5)

Nets for the canonical -dipyramids are illustrated above for to 10.

Johnson solid is a triangular dipyramid, the octahedron is a square dipyramid, and Johnson solid is a pentagonal dipyramid.