Chapter 12: Analytical Trigonometry
In section Section 11.4, we first encountered the concept of an identity when discussing Theorem 11.7. Recall that an identity is an equation which is true regardless of the choice of variable. Identities are important in mathematics because they facilitate changing forms.
We take a moment to generalize Theorem 11.7 below.
Adapted from Precalculus with Integrated Calculus, edition 4i, by Carl Stitz and Jeff Zeager (stitz-zeager.com), licensed under CC BY-NC-SA 3.0. Changes were made: reformatted as an accessible XYZ web edition. License: CC-BY-NC-SA-3.0.