|Bowers style acronym||Det|
|Faces||20 isosceles triangles|
|Vertex figure||2 decagons, 10 squares|
|Measures (edge length 1)|
|Number of external pieces||20|
|Level of complexity||3|
|Abstract & topological properties|
|Symmetry||I2(10)×A1, order 40|
The decagonal tegum, also called a decagonal bipyramid, is a tegum with a decagon as the midsection, constructed as the dual of a decagonal prism. It has 20 isosceles triangles as faces, with 2 order–10 and 10 order–4 vertices.
In the variant obtained as the dual of a uniform decagonal prism, the side edges are times the length of the edges of the base decagon. Each face has apex angle and base angles . If the base decagon has edge length 1, its height is .