cosine Meaning, Definition & Usage

  1. noun ratio of the adjacent side to the hypotenuse of a right-angled triangle
    cos.

WordNet

Co"sine noun
Etymology
For co. sinus, an abbrev. of L. complementi sinus.
Definitions
  1. (Trig.) The sine of the complement of an arc or angle. See Illust. of Functions.

Webster 1913