# cosine

[ koh-sahyn ]

/ ˈkoʊ saɪn /

### 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).

## QUIZZES

#### QUIZ YOURSELF ON THESE WORDS FROM BROWN GIRL DREAMING!

Visualize yourself passing this quiz on words from Jacqueline Woodson’s exquisite verse novel “Brown Girl Dreaming,” and then take the quiz to prove you can do it! (Because you can.)

Question 1 of 10

What does “barren” mean?

## Words nearby cosine

cosign, cosignatory, cosigner, Cosimo, Cosimo I, cosine, COSLA, cos lettuce, cosm-, cosmeceutical, Cosmegen

Dictionary.com Unabridged
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2020

## Example sentences from the Web for cosine

## 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.