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. 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)

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