Cosine
Pronunciation: /ˈkoʊ.saɪn/ Explain
Abbreviation: cos
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 Manipulative 1  Cosine Created with GeoGebra. 

In right triangle trigonometry, the Cosine is
defined to be equal to the length of the side adjacent to the angle
divided by the length of the hypotenuse.^{[2]}
On the
unit circle,
cosine is the directed distance of a point on the unit circle from the yaxis.
The
inverse of the cosine function
is the arccosine function. The
arccosine function can be written as arccos()
or cos^{1}().

References
 McAdams, David E.. All Math Words Dictionary, cosine. 2nd Classroom edition 201501084799968. pg 49. Life is a Story Problem LLC. January 8, 2015. Buy the book
 Fine, Henry B., Ph. D.. NumberSystem of Algebra Treated Theoretically and Historically. 2nd edition. pp 28,47. www.archive.org. D. C. Heath & Co., Boston, U.S.A.. 1907. Last Accessed 6/25/2018. http://www.archive.org/stream/thenumbersystemo17920gut/17920pdf#page/n37/mode/1up/search/cosine. Buy the book
 Hutton, Charles. A Course in Mathematics, Volume II. 4th edition. pp 23. www.archive.org. G. & J. Robinson. 1804. Last Accessed 6/25/2018. http://www.archive.org/stream/courseofmathemat02huttrich#page/2/mode/1up/search/cosecant. Buy the book
More Information
 McAdams, David E.. Secant. allmathwords.org. All Math Words Encyclopedia. Life is a Story Problem LLC. 6/27/2018. http://www.allmathwords.org/en/s/secant.html.
Cite this article as:
McAdams, David E. Cosine. 4/16/2019. All Math Words Encyclopedia. Life is a Story Problem LLC. http://www.allmathwords.org/en/c/cosine.html.
Image Credits
Revision History
4/16/2019: Updated equations and expressions to new format. (
McAdams, David E.)
12/21/2018: Reviewed and corrected IPA pronunication. (
McAdams, David E.)
6/25/2018: Removed broken links, updated license, implemented new markup, updated GeoGebra apps. (
McAdams, David E.)
1/5/2010: Expanded "References". (
McAdams, David E.)
12/19/2009: Added "References". (
McAdams, David E.)
12/2/2008: Added reference to arccosine. (
McAdams, David E.)
10/30/2008: Changed manipulative to GeoGebra. (
McAdams, David E.)
4/30/2008: Initial version. (
McAdams, David E.)