# Decagon

Pronunciation: /ˈdɛk.əˌgɒn/ Explain

 Click on the blue points and drag them to change the figure. Manipulative 1 - Regular Decagon Created with GeoGebra.

A decagon is a ten sided polygon.[2] A regular decagon is a ten sided regular polygon. In table 1, a is the length of a side and n is the number of sides.

Formula for regular decagon
Number of sides
Central angle
Area
Interior angle
Exterior angle
Table 1

### Geometric Nets

A geometric net is a 2-dimensional shape that folds into a 3-dimensional polyhedron. Some geometric nets that contain at least 1 decagon are shown in table 2.

ImageDescription
Net of a decagonal frustum.
Net of a decagonal antiprism.
Net of a decagonal prism.
Net of a pentagonal cupola.
Net of a pentagonal rotunda.
Net of a truncated dodecahedron.
Net of a truncated icosidodecahedron.
Table 2: Geometric nets that contain decagons.

### References

1. McAdams, David E.. All Math Words Dictionary, decagon. 2nd Classroom edition 20150108-4799968. pg 54. Life is a Story Problem LLC. January 8, 2015. Buy the book
2. Venugopal, Valsaraj. Higher Elementary Geometry. www.archive.org. 1st edition. pg 5. Last Accessed 7/3/2018. http://www.archive.org/stream/higherelementary033043mbp#page/n20/mode/1up/search/decagon. Buy the book
3. Hornbrook, A. R.. Concrete geometry for beginners. pg 127. www.archive.org. American Book Company. 1895. Last Accessed 7/3/2018. http://www.archive.org/stream/concretegeometry00hornrich#page/127/mode/1up/search/decagon. Buy the book

• McAdams, David E.. Geometric Nets. lifeisastoryproblem.com. Life is a Story Problem LLC. 3/12/2009. http://www.lifeisastoryproblem.com/explore/index_net.html.

McAdams, David E. Decagon. 12/21/2018. All Math Words Encyclopedia. Life is a Story Problem LLC. http://www.allmathwords.org/en/d/decagon.html.

### Revision History

12/21/2018: Reviewed and corrected IPA pronunication. (McAdams, David E.)