Cuboid
{{#invoke:Hatnote|hatnote}} In geometry, a cuboid is a convex polyhedron bounded by six quadrilateral faces, whose polyhedral graph is the same as that of a cube. While mathematical literature refers to any such polyhedron as a cuboid,^{[1]} other sources use "cuboid" to refer to a shape of this type in which each of the faces is a rectangle (and so each pair of adjacent faces meets in a right angle); this more restrictive type of cuboid is also known as a rectangular cuboid, right cuboid, rectangular box, rectangular hexahedron, right rectangular prism, or rectangular parallelepiped.^{[2]}
General cuboids
By Euler's formula the number of faces ('F'), vertices (V), and edges (E) of any convex polyhedron are related by the formula "F + V " = E + 2 . In the case of a cuboid this gives 6 + 8 = 12 + 2; that is, like a cube, a cuboid has 6 faces, 8 vertices, and 12 edges.
Along with the rectangular cuboids, any parallelepiped is a cuboid of this type, as is a square frustum (the shape formed by truncation of the apex of a square pyramid).
Rectangular cuboid
Rectangular cuboid | |
---|---|
Type | Prism |
Faces | 6 rectangles |
Edges | 12 |
Vertices | 8 |
Symmetry group | D_{2h}, [2,2], (*222), order 8 |
Schläfli symbol | { }×{ }×{ } or { }^{3} |
Coxeter diagram | Template:CDD |
Dual polyhedron | Rectangular fusil |
Properties | convex, zonohedron, isogonal |
In a rectangular cuboid, all angles are right angles, and opposite faces of a cuboid are equal. By definition this makes it a right rectangular prism, and the terms rectangular parallelepiped or orthogonal parallelepiped are also used to designate this polyhedron. The terms "rectangular prism" and "oblong prism", however, are ambiguous, since they do not specify all angles.
The square cuboid, square box, or right square prism (also ambiguously called square prism) is a special case of the cuboid in which at least two faces are squares. It has Schläfli symbol {4}×{ }, and its symmetry is doubled from [2,2] to [4,2], order 16.
The cube is a special case of the square cuboid in which all six faces are squares. It has Schläfli symbol {4,3}, and its symmetry is raised from [2,2], to [4,3], order 48.
If the dimensions of a rectangular cuboid are a, b and c, then its volume is abc and its surface area is 2ab + 2ac + 2bc.
The length of the space diagonal is
Cuboid shapes are often used for boxes, cupboards, rooms, buildings, etc. Cuboids are among those solids that can tessellate 3-dimensional space. The shape is fairly versatile in being able to contain multiple smaller cuboids, e.g. sugar cubes in a box, boxes in a cupboard, cupboards in a room, and rooms in a building.
A cuboid with integer edges as well as integer face diagonals is called an Euler brick, for example with sides 44, 117 and 240. A perfect cuboid is an Euler brick whose space diagonal is also an integer. It is currently unknown whether a perfect cuboid actually exists.
See also
References
External links
- Weisstein, Eric W., "Cuboid", MathWorld.
- Rectangular prism and cuboid Paper models and pictures