Cuboid

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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 some 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[edit]

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[edit]

Rectangular cuboid
Rectangular cuboid
Type Prism
Faces 6 rectangles
Edges 12
Vertices 8
Symmetry group D2h, [2,2], (*222), order 8
Schläfli symbol { }×{ }×{ } or { }3
Coxeter diagram CDel node 1.pngCDel 2.pngCDel node 1.pngCDel 2.pngCDel node 1.png
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. It is also a right rectangular prism. The term "rectangular or oblong prism" is ambiguous. Also the term rectangular parallelepiped or orthogonal parallelepiped is used.

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. The cube is a special case of the square cuboid in which all six faces are squares.

If the dimensions of a 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

d = \sqrt{a^2+b^2+c^2}.\

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[edit]

References[edit]

  1. ^ Robertson, Stewart Alexander (1984), Polytopes and Symmetry, Cambridge University Press, p. 75, ISBN 978-0-521-27739-6 
  2. ^ Dupuis, Nathan Fellowes (1893), Elements of Synthetic Solid Geometry, Macmillan, p. 53 

External links[edit]