查看“︁雙錐體”︁的源代码

{{NoteTA|G1=Math}}
{{Infobox polyhedron
| name = 雙錐體
| polyhedron = 雙錐體
| imagename = Hexagonale bipiramide.png
| caption = 以雙六角錐為例
| Type = 雙錐體
| Coxeter_diagram = {{CDD|node_f1|2|node_f1|n|node}}
| Face=2⋅n
| Edge=3⋅n
| Vertice=n+2
| variable=n
| variable_dest=底面邊數
| Face_type = [[三角形]]
| Vertice_type = V4.4.''n''
| Vertice_configuration = 
| Schläfli = { } + {n}
| Wythoff = 
| Face_configuration = 
| Conway = 
| Symmetry_group = [[Dihedral symmetry in three dimensions|D<sub>''n''h</sub>]], [''n'',2], (*''n''22), order 4''n''
| Index_references = 
| dual = [[柱體|n角柱]]
| Rotation_group = D<sub>''n''</sub>, [''n'',2]<sup>+</sup>, (''n''22), order 2''n''
| Dihedral_angle = 
| Properties = 凸、 [[面可遞]]
| 3d_image = 
| vfigimage = 
| dual_image = Hexagonal Prism BC.svg
| net_image = Generalized bipyramid net.svg
}}
'''雙錐體'''，或'''雙稜錐'''、又稱'''雙角錐'''，是一種幾何體，是由一[[錐體]]，經底面[[反射 (数学)|鏡射]]產生的[[幾何變換|像]]和原本的錐體合成的立體，換句話說，雙錐體就是將兩個相同的[[錐體]]背對背、底面對[[底面]]黏起來。其也是[[柱體]]的[[對偶多面體]]，將一[[柱體]]每面的[[幾何中心|重心]]當作新的頂點做成多面體也可得到'''雙錐體'''。

一般雙錐體會命名為類似'''雙n角錐'''的名稱，不是因為它有一個[[多邊形|n邊形]]的[[面 (幾何)|面]]，而是因為它的橫[[截面 (幾何)|切面]]是[[多邊形|n邊形]]，或說它是由[[稜錐|n角錐]]疊成的。

每面全等的'''雙n角錐'''是[[柱體|正n角體]]的對偶多面體，這樣子的雙錐的面通常是[[等腰三角形]]。

== 體積 ==
雙錐的體積<math>\scriptstyle{V =} \tfrac{2}{3} \scriptstyle{Bh}</math>，其中B是中央切面的面積，基座的面積；h是基座到頂點的高度。

正雙錐的體積，基座的正n邊形長度為s，基座到頂點的高度為h，則有：
:<math>V = \frac{n}{6}hs^2 \cot\frac{\pi}{n}.</math>

== 詹森雙錐 ==
{{main|约翰逊多面体#雙錐}}
在所有雙錐中，有3個雙錐全部都由正多邊形組成，分別為[[雙三角錐]]、[[雙四角錐]]和[[雙五角錐]]；[[雙六角錐]]退化成一個平面。

雙三角錐和雙五角錐屬於[[詹森多面體]]；雙四角錐屬於正多面體，因此不屬於詹森多面體。
{|
|- align="center" valign="bottom" 
|[[Image:Triangular dipyramid.png|100px]]
|[[Image:octahedron.svg|100px]]
|[[Image:Pentagonal dipyramid.png|100px]]
|- align="center" valign="top" 
|[[雙三角錐]]
|[[雙四角錐]]<BR>（[[正八面體]]）
|[[雙五角錐]]
|}

== 參考來源 ==
*{{mathworld |urlname=Dipyramid |title=Dipyramid}}
*{{GlossaryForHyperspace |anchor=Bipyramid |title=Bipyramid}}
*[http://www.mathconsult.ch/showroom/unipoly/ The Uniform Polyhedra] {{Wayback|url=http://www.mathconsult.ch/showroom/unipoly/ |date=20080211233246 }}
*[http://www.georgehart.com/virtual-polyhedra/vp.html Virtual Reality Polyhedra] {{Wayback|url=http://www.georgehart.com/virtual-polyhedra/vp.html |date=20080223132026 }} The Encyclopedia of Polyhedra
**[[VRML]] models [http://www.georgehart.com/virtual-polyhedra/alphabetic-list.html (George Hart)] {{Wayback|url=http://www.georgehart.com/virtual-polyhedra/alphabetic-list.html |date=20051225041422 }} [http://www.georgehart.com/virtual-polyhedra/vrml/triangular_dipyramid.wrl <3>] {{Wayback|url=http://www.georgehart.com/virtual-polyhedra/vrml/triangular_dipyramid.wrl |date=20210427014514 }} [http://www.georgehart.com/virtual-polyhedra/vrml/octahedron.wrl <4>] {{Wayback|url=http://www.georgehart.com/virtual-polyhedra/vrml/octahedron.wrl |date=20201231095928 }} [http://www.georgehart.com/virtual-polyhedra/vrml/pentagonal_dipyramid.wrl <5>] {{Wayback|url=http://www.georgehart.com/virtual-polyhedra/vrml/pentagonal_dipyramid.wrl |date=20200723151640 }} [http://www.georgehart.com/virtual-polyhedra/vrml/hexagonal_dipyramid.wrl <6>] {{Wayback|url=http://www.georgehart.com/virtual-polyhedra/vrml/hexagonal_dipyramid.wrl |date=20210414131958 }} [https://web.archive.org/web/20150203062131/http://www.georgehart.com/virtual-polyhedra/vrml/heptagonal_dipyramid.wrl <7>] [http://www.georgehart.com/virtual-polyhedra/vrml/octagonal_dipyramid.wrl <8>] {{Wayback|url=http://www.georgehart.com/virtual-polyhedra/vrml/octagonal_dipyramid.wrl |date=20200420092938 }} [http://www.georgehart.com/virtual-polyhedra/vrml/enneagonal_dipyramid.wrl <9>] {{Wayback|url=http://www.georgehart.com/virtual-polyhedra/vrml/enneagonal_dipyramid.wrl |date=20200417002436 }} [http://www.georgehart.com/virtual-polyhedra/vrml/decagonal_dipyramid.wrl <10>] {{Wayback|url=http://www.georgehart.com/virtual-polyhedra/vrml/decagonal_dipyramid.wrl |date=20210427040752 }}
***[http://www.georgehart.com/virtual-polyhedra/conway_notation.html Conway Notation for Polyhedra] {{Wayback|url=http://www.georgehart.com/virtual-polyhedra/conway_notation.html |date=20141129085342 }} Try: "dP'''n'''", where '''n''' = 3, 4, 5, 6, ... example "dP4" is an octahedron.

{{錐體與柱體}}
{{Convex polyhedron navigator}}

[[category:雙錐]]