CK-12 Trigonometry: Second Edition

A complete college course that builds trigonometry from angles and the unit circle to identities, inverse functions, polar coordinates and vectors. Clear worked examples and hundreds of exercises with answers make it ideal for self-study.

Carl Stitz, Jeff Zeager

A modern open textbook from Grand Valley State University that teaches trigonometry through active learning, with preview activities, clear explanations and exercises in every section. Covers the unit circle, graphs, identities, triangles and vectors.

Ted Sundstrom, Steven Schlicker

A full college trigonometry textbook built by four Utah universities and adapted from Stitz and Zeager. It covers angles, the unit circle, graphs, identities, equations and the laws of sines and cosines, with plenty of practice problems.

Salt Lake Community College

A concise and rigorous open textbook that covers right triangles, general triangles, identities, graphs, inverse functions and complex numbers. Every chapter ends with exercises, and answers to selected problems are included.

Michael Corral

A complete course built around applications and guided investigations, from triangle trigonometry to the unit circle, radians, identities, vectors and polar coordinates. Includes hundreds of exercises and clear graphs.

Katherine Yoshiwara