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# cosine

[ koh-sahyn ]

/ ˈkoʊ saɪn /

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noun

Trigonometry.

- (in a right triangle) the ratio of the side adjacent to a given angle to the hypotenuse.
- the sine of the complement of a given angle or arc. Abbreviation: cos

Mathematics. (of a real or complex number x) the function cos x defined by the infinite series 1 − (x2/2!) + (x4/4!) − + …, where ! denotes factorial. Abbreviation: cosCompare sine (def. 3), factorial (def. 1).

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## Words nearby cosine

cosign, cosignatory, cosigner, Cosimo, Cosimo I, cosine, COSLA, cos lettuce, cosm-, cosmetic, cosmetician

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Based on the Random House Unabridged Dictionary, © Random House, Inc. 2022

## How to use cosine in a sentence

## British Dictionary definitions for cosine

cosine

/ (ˈkəʊˌsaɪn) /

noun (of an angle)

a trigonometric function that in a right-angled triangle is the ratio of the length of the adjacent side to that of the hypotenuse; the sine of the complementAbbreviation: cos

## Word Origin for cosine

C17: from New Latin cosinus; see co-, sine 1

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

## Scientific definitions for cosine

cosine

[ kō′sīn′ ]

The ratio of the length of the side adjacent to an acute angle of a right triangle to the length of the hypotenuse.

The abscissa of the endpoint of an arc of a unit circle centered at the origin of a Cartesian coordinate system, the arc being of length x and measured counterclockwise from the point (1, 0) if x is positive or clockwise if x is negative.

A function of a number x, equal to the cosine of an angle whose measure in radians is equal to x.

The American Heritage® Science Dictionary
Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.