any of a group of functions of an angle expressed as a ratio of two of the sides of a right-angled triangle containing the angle. The group includes sine, cosine, tangent, secant, cosecant, and cotangent
2.
any function containing only sines, cosines, etc, and constants
trigonometric function in American English
any of the basic functions (as sine, cosine, tangent, etc.) of an angle or arc, usually expressed as the ratio of pairs of sides of a right triangle