trigonometric function

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. 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, and cosecant. Also called circular function.

Wiktionary

1. n. 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)

WordNet 3.0

1. n. function of an angle expressed as a ratio of the length of the sides of right-angled triangle containing the angle