Dictionary
co•sine
Pronunciation: (kō'sīn), [key]—
n.
1. Trigonom.
a. (in a right triangle) the ratio of the side adjacent to a given angle to the hypotenuse.
b. the sine of the complement of a given angle or arc.
Abbr.: cos
2. Math.(of a real or complex number
x) the function cos
x defined by the infinite series 1 - (
x2/2!) + (
x4/4!) - + … , where ! denotes factorial.
Abbr.: cos Cf.
sine (def. 3),
factorial (def. 1).
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.