Meaning of cosine

co•sine

Pronunciation: (kō'sīn), [key]
— n.
    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. Abbr.: cos
  1. (of a real or complex number x) the function cos x defined by the infinite series 1 − (x/2!) + (x/4!) − + … , where ! denotes factorial. Abbr.: cos Cf. sine (def. 3),(def. 1).
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.
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