For the academic journal, see Tetrahedron (journal).
Regular Tetrahedron
(Click here for rotating model)
Type Platonic solid
Elements F = 4, E = 6
V = 4 (χ = 2)
Faces by sides 4{3}
Schläfli symbol {3,3} and s{2,2}
Wythoff symbol 3 | 2 3
| 2 2 2
Coxeter-Dynkin CDW ring.pngCDW 3.pngCDW dot.pngCDW 3.pngCDW dot.png
CDW hole.pngCDW 2c.pngCDW hole.pngCDW 2c.pngCDW hole.png
CDW hole.pngCDW 4.pngCDW dot.pngCDW 2c.pngCDW hole.png
CDW hole.pngCDW 4.pngCDW dot.pngCDW 3.pngCDW dot.png
Symmetry Td
or (*332)
References U01, C15, W1
Properties Regular convex deltahedron
Dihedral angle 70.528779° = arccos(1/3)
(Vertex figure)
(dual polyhedron)

A tetrahedron (plural: tetrahedra) is a polyhedron composed of four triangular faces, three of which meet at each vertex. A regular tetrahedron is one in which the four triangles are regular, or "equilateral", and is one of the Platonic solids.

The tetrahedron is one kind of pyramid, which is a polyhedron with a flat polygon base and triangular faces connecting the base to a common point. In the case of a tetrahedron the base is a triangle (any of the four faces can be considered the base), so a tetrahedron is also known as triangular pyramid or Digonal Deltahedron.

Formulas for regular tetrahedron

The volume is

The surface area is

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