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
Double Angle Formulas
Power-Reducing/Half Angle 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.
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.