Dipyramids & Trapezohedra

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Octagonal Dipyramid
Vertices:  10  (8[4] + 2[8])
Faces:16  (isosceles triangles)
Edges:24  (8 short + 16 long)
Symmetry:  8-fold Prismatic  (D8h)
Dihedral Angle:  acos(−(7+4*sqrt(2))/17)    ≈138.117959056 degrees
Dual Solid:  Octagonal Prism
(values below based on unit-edge-length Octagonal Prism)
Short Edge (8):  sqrt(2*(2−sqrt(2)))    ≈1.0823922002923939688
Long Edge (16):  2*sqrt(2+sqrt(2))    ≈3.69551813004514702451
[4]-Vertex Radius (8):  sqrt(2)    ≈1.4142135623730950488
[8]-Vertex Radius (2):  2+sqrt(2)    ≈3.4142135623730950488
Edge-scribed Radius:  sqrt(2*(2+sqrt(2)))/2    ≈1.3065629648763765279
Inscribed Radius:  sqrt(34*(7+4*sqrt(2)))/17    ≈1.2202629537976100741
Volume:16*(1+sqrt(2))/3    ≈12.875805665989840260