Dictionary.com

cosine

[ koh-sahyn ]
/ ˈkoʊ saɪn /
Save This Word!

noun
Trigonometry.
  1. (in a right triangle) the ratio of the side adjacent to a given angle to the hypotenuse.
  2. 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).
QUIZ
QUIZ YOURSELF ON AFFECT VS. EFFECT!
In effect, this quiz will prove whether or not you have the skills to know the difference between “affect” and “effect.”
Question 1 of 7
The rainy weather could not ________ my elated spirits on my graduation day.
Meet Grammar CoachWrite or paste your essay, email, or story into Grammar Coach and get grammar helpImprove Your Writing
Meet Grammar CoachImprove Your Writing
Write or paste your essay, email, or story into Grammar Coach and get grammar help

Origin of cosine

1625–35; <New Latin cosinus. See co-, sine
Dictionary.com Unabridged 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
[ kōsīn′ ]

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.
FEEDBACK