the reciprocal of the secant; specif.
- the ratio of the adjacent side of a given acute angle in a right triangle to the hypotenuse
- an equivalent, positive or negative ratio for certain related angles (Ex.: the cosine of 57° or 303° is .5446, of 123° or 237° is -.5446) or real numbers representing radians (Ex.: cosine of .9948 radians (57°) is .5446)
ModL < co. sinus, short for complementi sinus, lit., sine of the complement