Also called: circular functionany 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

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.