Cosine
Pronunciation: /ˈkoʊ saɪn/ Explain
Abbreviation: cos
Click on the blue points and drag them to change the figure.
 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.^{[1]}
On the
unit circle,
cosine is the directed distance of a point on the unit circle from the yaxis. Click
on the blue point in manipulative 1 and drag it to change the figure.
The
inverse of the cosine function
is the arccosine function. The
arccosine function can be written as
or .

References
 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 8/6/2018. 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 8/6/2018. 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. 6/25/2018. All Math Words Encyclopedia. Life is a Story Problem LLC. http://www.allmathwords.org/en/c/cosine.html.
Image Credits
Revision History
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.)