9邊形的英文(XXgon)(20分)

Nonagon From Wikipedia, the free encyclopedia (Redirected from Enneagon) Jump to: navigation, search Regular nonagon
圖片參考：http://upload.wikimedia.org/wikipedia/commons/f/fc/CDW_dot.png
Symmetry group Dihedral (D9) Area
(with t=edge length
圖片參考：http://upload.wikimedia.org/math/3/9/8/3985b0210efa83e06b2d2c3f1c50694b.png
Internal angle
(degrees) 140° In geometry, a nonagon (or enneagon) is a nine-sided polygon.
The name "nonagon" is a hybrid formation, from Latin (nonus, "ninth" + gonon), used equivalently, attested already in the 16th century in French nonogone and in English from the 17th century. The name "enneagon" comes from Greek enneagonon, (εννεα, nine + γωνον, corner), and is arguably more correct, though somewhat less common.
A regular nonagon has internal angles of 140°. The area of a regular nonagon of side length a is given by

圖片參考：http://upload.wikimedia.org/math/1/d/f/1dff371d0337799aacb75c0a22e69aeb.png
Although a regular nonagon is not constructible with compass and straightedge there are methods of constructing that are very close approximations.
Contents [hide] 1 Graphs and stars2 See also3 References4 External links
[edit] Graphs and stars The K9 complete graph is often drawn as a regular nonagon with all 36 edges connected. This graph also represents an orthographic projection of the 9 vertices and 36 edges of the 8-simplex.

圖片參考：http://upload.wikimedia.org/wikipedia/en/thumb/9/92/Complete_graph_K9.svg/160px-Complete_graph_K9.svg.png

The regular nonagon also contains 3 star figures, the third being the compound of three equilateral triangles:

圖片參考：http://upload.wikimedia.org/wikipedia/en/thumb/1/15/Star_figure_9-3.png/150px-Star_figure_9-3.png


[edit] See also GeometryTrigonometryPolygonNonagonal numberEnneagramEnneagram of Personality
[edit] References Eric W. Weisstein, Nonagon at MathWorld.
[edit] External links Properties of a Nonagon With interactive animation [hide] v • d • e Polygons Triangle · Quadrilateral · Pentagon · Hexagon · Heptagon · Octagon · Enneagon (Nonagon) · Decagon · Hendecagon · Dodecagon · Triskaidecagon · Pentadecagon · Hexadecagon · Heptadecagon · Enneadecagon · Icosagon · Chiliagon · Myriagon Retrieved from "http://en.wikipedia.org/wiki/Nonagon" Category: Polygons

九邊形有兩個名稱，分別是nonagon和enneagon。

The name "nonagon" is a hybrid formation, from Latin (nonus, "ninth" + gonon), used equivalently, attested already in the 16th century in French nonogone and in English from the 17th century. The name "enneagon" comes from Greek enneagonon, (εννεα, nine + γωνον, corner), and is arguably more correct, though somewhat less common.


n-side polygon是可以用的，不過n-gon似乎更加多人使用。
另外，各種邊數的多邊形的正式名稱不妨可以認識一下，但無需要全部記哂。

Individual polygons are named (and sometimes classified) according to the number of sides, combining a Greek-derived numerical prefix with the suffix -gon, e.g. pentagon, dodecagon. The triangle, quadrilateral, and nonagon are exceptions. For large numbers, mathematicians usually write the numeral itself, e.g. 17-gon. A variable can even be used, usually n-gon. This is useful if the number of sides is used in a formula.






Polygon names



Name


Edges



henagon (or monogon)


1



digon


2



triangle (or trigon)


3



quadrilateral (or tetragon)


4



pentagon


5



hexagon


6



heptagon (avoid "septagon" = Latin [sept-] + Greek)


7



octagon


8



enneagon (or nonagon)


9



decagon


10



hendecagon (avoid "undecagon" = Latin [un-] + Greek)


11



dodecagon (avoid "duodecagon" = Latin [duo-] + Greek)


12



tridecagon (or triskaidecagon)


13



tetradecagon (or tetrakaidecagon)


14



pentadecagon (or quindecagon or pentakaidecagon)


15



hexadecagon (or hexakaidecagon)


16



heptadecagon (or heptakaidecagon)


17



octadecagon (or octakaidecagon)


18



enneadecagon (or enneakaidecagon or nonadecagon)


19



icosagon


20



No established English name
"hectogon" is the Greek name
"centagon" is a Latin-Greek hybrid; neither is widely attested.


100



chiliagon


1000



myriagon


10,000



googolgon


10100


To construct the name of a polygon with more than 20 and less than 100 edges, combine the prefixes as follows:





Tens


and


Ones


final suffix



-kai-


1


-hena-


-gon



20


icosi-


2


-di-



30


triaconta-


3


-tri-



40


tetraconta-


4


-tetra-



50


pentaconta-


5


-penta-



60


hexaconta-


6


-hexa-



70


heptaconta-


7


-hepta-



80


octaconta-


8


-octa-



90


enneaconta-


9


-ennea-


The 'kai' is not always used. Opinions differ on exactly when it should, or need not, be used (see also examples above).

That is, a 42-sided figure would be named as follows:





Tens


and


Ones


final suffix


full polygon name



tetraconta-


-kai-


-di-


-gon


tetracontakaidigon

and a 50-sided figure





Tens


and


Ones


final suffix


full polygon name



pentaconta-





-gon


pentacontagon

９邊形係Nonagon

Nawes of Polygons
Triangle (3 sided)
Quadrilateral (4 sided)
Pentagon (5sided)
Hexagon (6 sided)
Heptagon (7 sided)
Octagon (8 sided)
Nonagon (9 sided)
Decagon (10 sided)
n-gon (n sided)

九邊形：nonagon
十邊形：decagon

10條邊以上的多邊形的英文是不是叫x-side polygon?--> Yeah, they can be named this way.

Nonagon