- the ratio of the adjacent side of a given acute angle in a right triangle to the opposite side
- an equivalent, positive or negative ratio for certain related angles (Ex.: the cotangent of 57° or 237° is .6494, of 123° or 303° is ?.6494) or real numbers representing radians (Ex.: the cotangent of .9948 radians (57°) is .6494)

Origin of cotangent

Modern Latin*cotangens*from

*co. tangens,*short for

*complementi tangens,*literally , tangent of the complement