DefinitionTrigonometry is the study of the properties of triangles with a specific emphasis on the angle measures and side lengths of right triangles. The four main functions are sine, cosine, tangent, and their reciprocal cotangent (cosine, sine, and secant are all reciprocals, and cosecant is the inverse of sine). This means that, for a right triangle with an angle θ, sin(θ)=hypotenuseopposite, cos(θ)=hypotenuseadjacent, and tan(θ)=adjacentopposite