Trigonometric Formula

Useful trig formulas and some very helpful links for learning trigonometric concepts.

Triangle ABC is any triangle with side lengths a,b,c Law of Cosines Law of Sines Reciprocal identities Pythagorean Identities Quotient Identities Co-Function Identities Even-Odd Identities Sum-Difference Formulas Double Angle Formulas Power-Reducing/Half Angle Formulas Sum-to-Product Formulas Product-to-Sum Formulas  Circular functions In mathematics, the trigonometric functions (also called circular functions) are functions of an angle. They are used to relate the angles of a triangle to the lengths of the sides of a triangle. Trigonometric functions are important in the study of triangles and modeling periodic phenomena, among many other applications. Above--- Trigonometric function sinθ for selected angles θ, π − θ, π + θ, and 2π − θ in the four quadrants. (Bottom) Graph of sine function versus angle. Angles from the top panel are identified.