Trigonometric Identities and Equations: Introduction 
There are certain trigonometric identities known to be true. In this section, you will learn about these identities and how to use them in proofs. You will also use the identities to help solve trigonometric equations.
Make sure to download the following document and use it as a reference guide throughout this section. It is also a good idea to have your completed Unit Circle ready as a reference guide.
Click here to download the reference guide.
An identity is an equality between two expressions that is true for all values of a variable or variables. Therefore, a trigonometric identity is just an identity that has trigonometric expressions.