Trigonometry

Trigonometry starts with a triangle you can measure and ends with a wave that repeats forever. This textbook walks that whole path in four units: Triangle Geometry, The Unit Circle, Periodic Functions, and Solving Trigonometric Equations.

It is built to be worked, not just read. Twenty-one teaching sections each open with a concrete situation and work the idea all the way through, then hand you practice backed by 606 hints you can open one at a time when you are stuck, and 378 fully worked solutions for when you want to check the whole thing. Every unit closes with a mixed-practice set and a recap checkpoint. Behind the course sit two appendices: an algebra review covering the seven skills trigonometry assumes you already have, and a study-tools set with the notation, glossary, methods, formulas, and identities gathered in one place.

Accessibility is built in, not bolted on. All 14,093 mathematical expressions are real MathML carrying a spoken-English label, so VoiceOver reads a formula as a sentence instead of spelling it out symbol by symbol. Of the 114 figures, 102 carry a full written description of what the diagram shows, reachable from the figure itself. Text is selectable and resizable, navigation is structural, and color contrast meets WCAG AA in both the light and dark palettes.

The twelve interactive widgets appear here as still images with descriptive captions. The live versions run in the free web edition at trigonometry.megan-warren.com.

Written for grades 10 to 12, and for anyone coming back to trigonometry on their own. 2026-2027 edition.