Trigonometry The word trigonometry comes from the Greek words trigonon (“triangle”) and metron (“to measure”). T rigonometry , the branch of mathematics that deals with specific functions of angles and their application. Basic functions There are six functions of an angle commonly used in trigonometry. They are tabulated below. Functions Abbreviation Relationship to sides of a right triangle Sine Function Sin θ Opposite side/ Hypotenuse Tangent Function Tan θ Opposite side / Adjacent side Cosine Function Cos θ Adjacent side / Hypotenuse Cosecant Function cosec θ Hypotenuse / Opposite side Secant Function sec θ Hypotenuse / Adjacent side Cotangent Function cot θ Adjacent side / O...