en.wikipedia.org/wiki/List_of_trigonometric_identities

In mathematics, trigonometric identities are equalities that involve trigonometric functions and are true for every single value of the occurring variables where ...

www.sosmath.com/trig/Trig5/trig5/trig5.html

Reciprocal identities. displaymath161. Pythagorean Identities. displaymath162. Quotient Identities. displaymath163. Co-Function Identities. displaymath164.

www.purplemath.com/modules/idents.htm

Lists the basic trigonometric identities, and specifies the set of trig identities to keep track of, as being the most useful ones for calculus.

math2.org/math/trig/identities.htm

sin(theta) = a / c. csc(theta) = 1 / sin(theta) = c / a. cos(theta) = b / c. sec(theta) = 1 / cos(theta) = c / b. tan(theta) = sin(theta) / cos(theta) = a / b. cot(theta) = 1/ ...

www.khanacademy.org/math/precalculus/trig-equations-and-identities-precalc/using-trig-identities-precalc/v/examples-using-pythagorean-identities-to-simplify-trigonometric-expressions

Rewrite trigonometric expressions using the Pythagorean identity and other trigonometric identities.

www.mathwords.com/t/trig_identities.htm

Trig Identities. Identities involving trig functions are listed below. Pythagorean Identities. sin2 θ + cos2 θ = 1. tan2 θ + 1 = sec2 θ. cot2 θ + 1 = csc2 θ ...

www.mathsisfun.com/algebra/trigonometric-identities.html

The Trigonometric Identities are equations that are true for Right Angled Triangles. (If it is not a Right Angled Triangle go to the Triangle Identities page.).

www.uhigh.ilstu.edu/math/sondgeroth/coll%20alg/09%20col%20alg%20notes%20072%20trig%20identities%20pt%202.htm

Basic Trig Identities – Sec. 7.1. sin x = cos x = tan x = tan x = csc x = = sec = = cot x = = cot x = Pythagorean Identities – Sec. 7.1. cos2 x + sin2 x = 1 cos2 x = 1 ...

www.themathpage.com/atrig/trigonometric-identities.htm

Pythagorean identities. Sum and difference formulas. Double angle formulas. Half angle formulas. Products as sums. Sums as products.

www2.clarku.edu/~djoyce/trig/identities.html

You have seen quite a few trigonometric identities in the past few pages. It is convenient to have a summary of them for reference. These identities mostly refer to ...