cosine

[ koh-sahyn ]

noun

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

cosine

/ ˈkəʊˌsaɪn /

noun

1. 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 complement cos

cosine

/ kō′sīn′ /

1. The ratio of the length of the side adjacent to an acute angle of a right triangle to the length of the hypotenuse.
2. 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.
3. A function of a number x , equal to the cosine of an angle whose measure in radians is equal to x.

Word History and Origins

Origin of cosine¹

1625–35; < New Latin cosinus. See co-, sine ( def )

Word History and Origins

Origin of cosine¹

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

Example Sentences

You can also use the cosine similarity here to compare content you have already seen with other products.

From Scientific American

These functions, such as the sine and cosine, are defined using right triangles.

From Scientific American

The mnemonic SO-CAH-TOA is commonly used to teach trigonometric functions sine, cosine and tangent.

From Washington Times

He proposed that all periodic functions — all periodic phenomena — could be understood as sums of sine and cosine waves.

From New York Times

And not once in the 40 years since I finished school have I ever been asked to factor a polynomial or calculate the cosine of anything.

From Los Angeles Times