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
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, or cosecant. Also called circular function.
In a right triangle, the three main trigonometric functions are
sine &thgr; = opposite / hypotenuse
cosine &thgr; = adjacent / hypotenuse
tangent &thgr; = opposite / adjacent.
(plural trigonometric functions)