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Acronym	tridpy (alt.: trit), J12
Name	trigonal dipyramid, (line-)triangle-tegum
VRML	⭳©
Vertex figure	[33], [34]
General of army	(is itself convex)
Colonel of regiment	(is itself locally convex)
Dihedral angles	between {3} and {3} (equatorial):   arccos(-7/9) = 141.057559° between {3} and {3} (lacing):   arccos(1/3) = 70.528779°
Face vector	5, 9, 6
Confer	uniform relative: tet   relatedJohnson solids: etidpy   variations: co oo3ox&#zy (c = y = 2/3,trip dual)  co oo3ox&#zy (c = sqrt(8)/3, y = sqrt(5)/3, ico derived)  co oo3ox&#zy (c = sqrt(2)/3, y = sqrt(7/18), tes derived)  co oo3ox&#zy (c = (sqrt(5)-1)/3, y = sqrt[(9-sqrt(5))/18], hi derived)   general polytopal classes: Johnson solids  deltahedra  bistratic lace towers
External links

Incidence matrix according toDynkin symbol

oxo3ooo&#xt   → both heights = sqrt(2/3) = 0.816497(pt|| pseudo {3}|| pt)o..3o..    |1 * * | 3 0 0 | 3 0.o.3.o.    | * 3 * | 1 2 1 | 2 2..o3..o    | * *1 | 0 0 3 | 0 3-----------+-------+-------+---oo.3oo.&#x | 1 1 0 | 3 * * | 2 0.x.3...    | 0 2 0 | * 3 * | 1 1.oo3.oo&#x | 0 1 1 | * * 3 | 0 2-----------+-------+-------+----ox.3...&#x | 1 2 0 | 2 1 0 | 3 *.xo3...&#x | 0 2 1 | 0 1 2 | * 3

oro..3o..     & |2 * | 3 0 | 3.o.3.o.       | * 3 | 2 2 | 4--------------+-----+-----+--oo.3oo.&#x  & | 1 1 | 6 * | 2.x.3...       | 0 2 | * 3 | 2--------------+-----+-----+--ox.3...&#x  & | 1 2 | 2 1 | 6

yo ox3oo&#zx   → height = 0   (y = sqrt(8/3) = 1.632993)(tegum product of line with {3})o. o.3o.    | 2 * | 3 0 | 3.o .o3.o    | * 3 | 2 2 | 4------------+-----+-----+--oo oo3oo&#x | 1 1 | 6 * | 2.. .x3.o    | 0 2 | * 3 | 2------------+-----+-----+--.. ox ..&#x | 1 2 | 2 1 | 6

oyo oox&#xt   → height(1,2) = 1/sqrt(3) = 0.577350                height(2,3) = 1/sqrt(12) = 0.288675                y = sqrt(8/3) = 1.632993(pt|| pseudo y-line|| perp line)o.. o..    |1 * * | 2 2 0 0 | 4 0.o. .o.    | * 2 * | 1 0 2 0 | 2 1..o ..o    | * * 2 | 0 1 2 1 | 2 2-----------+-------+---------+----oo. oo.&#x | 1 1 0 | 2 * * * | 2 0o.o o.o&#x | 1 0 1 | * 2 * * | 2 0.oo .oo&#x | 0 1 1 | * * 4 * | 1 1... ..x    | 0 0 2 | * * *1 | 0 2-----------+-------+---------+----ooo ooo&#x | 1 1 1 | 1 1 1 0 | 4 *... .ox&#x | 0 1 2 | 0 0 2 1 | * 2