For courses in Precalculus.

Ties concepts together using a functions approach 

Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry, 5th Edition introduces functions at the beginning of the text, then introduces and develops a new function in every chapter. Acclaimed authors Sullivan and Sullivan focus on the fundamentals (preparing for class, practicing with homework, and reviewing key concepts), which encourages students to master basic skills and develop the conceptual understanding needed for this and future courses. Graphing utility coverage is optional and can be adjusted at the instructor's discretion, based on course needs.