Hexagonal bipyramid bipyramid has a plane of symmetry (which is horizontal in the figure to the right) where the bases of the two pyramids are joined. This plane is a regular hexagon. There are also six planes of symmetry crossing through the two apices. These planes are rhombic and lie at 30° angles to each other, perpendicular to the horizontal plane. It can be drawn as a tiling on a sphere which also represents the fundamental domains of [3,2], *322 dihedral symmetry: The hexagonal bipyramid, dt{2,6}, can be in sequence truncated, tdt{2,6} and alternated (snubbed), sdt{2,6}: The "hexagonal bipyramid", dt{2,6}, can be
Magic hexagon gave a less intricate constructive proof. The order-3 magic hexagon has been published many times as a 'new' discovery. An early reference, and possibly the first discoverer, is Ernst von Haselberg (1887). The numbers in the hexagon are consecutive, and run from 1 to formula_1. Hence their sum is a triangular number, namely There are "r" = (2"n" − 1) rows running along any given direction (E-W, NE-SW, or NW-SE). Each of these rows sum up to the same number "M". Therefore: This can be rewritten as Multiplying throughout by 32 gives which shows that formula_6 must be an integer,