Trigonometry/Trigonometric identities

What is an identity?

An identity is an equation that holds true for all values of the variables appearing in it, because it either is a definition or is the logical consequence of a definition. An example of a definitional identity is $\tan(x)=\frac{\sin(x)}{\cos(x)}.$ An example of an identity that can logically be proven to hold for all values of its variable is the Pythagorean identity expressed in trigonometric form: sin²(x) + cos²(x) = 1.

Next Page: Graphs of Sine and Cosine Functions
Previous Page: Right Angle Trigonometry

Home: Trigonometry