cosine

[ koh-sahyn ]

Phonetic (Standard)IPA

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. : cos
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 /

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′ /

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.

Origin of cosine¹

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

Origin of cosine¹

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

And, seating himself beside Dirrik, he began to explain the mysteries of sine, cosine and tangent.

The sine and the cosine I shall have occasion to employ in the latter part of my lecture.

Like the functions sine and cosine, the elliptic functions have addition theorems, e.g.

Nevertheless, I bear no grudge against the sine and the cosine, which I continue to hold in high esteem.

The nine cosine-inclinations above are, as has been seen, connected by six equations.

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