Editing Triangular bipyramid (section)

{{Short description|Two tetrahedra joined by one face}}
{{good article}}
{{Infobox polyhedron
 | image = Triangular bipyramid.png
 | type =
 [[Bipyramid]]<br>[[Deltahedron|Deltahedra]]<br>[[Johnson solid|Johnson]]<br>
 {{math|[[gyroelongated pentagonal pyramid|''J''<sub>11</sub>]] – '''''J''<sub>12</sub>''' – [[Pentagonal bipyramid|''J''<sub>13</sub>]]}}<br>[[Noble polyhedron]]
 | faces = 6 [[triangle]]s
 | edges = 9
 | vertices = 5
 | vertex_config = <math> 3 \times (3^2) + 6 \times (3^2) </math>
 | symmetry = <math> D_{3 \mathrm{h}} </math>
 | dual = [[triangular prism]]
 | angle = As a Johnson solid:{{bulletlist
  | triangle-to-triangle: 70.5°
  | triangle-to-triangle if tetrahedrons being attached: 141.1°
  }}
 | properties = [[Convex set|convex]],<br>[[composite polyhedron|composite]],<br>[[face-transitive]]
}}
A '''triangular bipyramid''' is a [[hexahedron]] with six triangular faces constructed by attaching two [[Tetrahedron|tetrahedra]] face-to-face. The same shape is also known as a '''triangular dipyramid'''{{r|trigg|rajwade}} or '''trigonal bipyramid'''.{{r|king}} If these tetrahedra are regular, all faces of a triangular bipyramid are [[Equilateral triangle|equilateral]]. It is an example of a [[deltahedron]], [[composite polyhedron]], and [[Johnson solid]].

Many polyhedra are related to the triangular bipyramid, such as similar shapes derived from different approaches and the [[triangular prism]] as its [[dual polyhedron]]. Applications of a triangular bipyramid include [[trigonal bipyramidal molecular geometry]] which describes its [[atom cluster]], a solution of the [[Thomson problem]], and the representation of [[Color model|color order systems]] by the eighteenth century.