Bipyramide

Bipyramid is a term used in geometry to describe a polyhedron composed of two square pyramids (or any other quadrilateral pyramid) that share a common square base. The bipyramid can be considered as a special case of the more general truncated pyramid or frustum, where the top and bottom faces are squares.

The bipyramid has a total of 6 faces: 2 square faces at the top and bottom, and 4 triangular faces connecting them. It has 8 vertices and 12 edges. The bipyramid is a type of central polygon, meaning it has a central face (the square base) and all other faces meet at a single point (the apex of the pyramids).

The bipyramid is a type of Johnson solid, specifically J2. It is also related to the square dipyramid, which is a bipyramid with triangular faces instead of square faces. The bipyramid is not a Platonic solid, but it is a member of the Johnson solids, which are convex polyhedra with regular polygonal faces but are not necessarily uniform.

The bipyramid has applications in various fields, including architecture, where it is used as a design element in buildings, and in chemistry, where it is used to model molecular structures. It is also a popular subject in recreational mathematics and geometry puzzles.