Also called circular function. 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
A function of an angle, as the sine, cosine, or tangent, whose value is expressed as a ratio of two of the sides of the right triangle that contains the angle.