The Decagonal Prism
The decagonal prism is a 3D uniform polyhedron bounded by 2 decagonal faces and 10 squares. It has 30 edges and 20 vertices. It may be considered to be the extrusion of the decagon.
Attaching two cupolae to a decagonal prism produces the elongated pentagonal orthobicupola (J38) or the elongated pentagonal gyrobicupola (J39), depending on the orientation of the two cupolae relative to each other.
Attaching two pentagonal rotunda to a decagonal prism produces the elongated pentagonal orthobirotunda (J42) or the elongated pentagonal gyrobirotunda (J43), depending on the orientation of the rotundae with respect to each other.
In order to be able to identify the decagonal prism in various projections of 4D objects, it is useful to know how it appears from various viewpoints. The following are some of the commonly-encountered views:
Decagon-centered parallel projection.
Parallel projection centered on a vertical edge.
Square-centered parallel projection.
Vertex-centered parallel projection.
The Cartesian coordinates of the decagonal prism, centered on the origin and having edge length 2, are all changes of sign of:
- (2φ, 0, 1)
- (1, √(3+4φ), 1)
- (φ2, √(2+φ), 1)
where φ=(1+√5)/2 is the Golden Ratio.
The decagonal prism occurs in the following uniform polychora: