trigonometric function

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A function of an angle expressed as the ratio of two of the sides of a right triangle that contains that angle; the sine, cosine, tangent, cotangent, secant, or cosecant.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun trigonometry Any function of an angle expressed as the ratio of two of the sides of a right triangle that has that angle, or various other functions that subtract 1 from this value or subtract this value from 1 (such as the versed sine)

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun function of an angle expressed as a ratio of the length of the sides of right-angled triangle containing the angle