Introduction to Trigonometry: Right-Angled Triangles

A clear review of the essential topics: angle measurement, the unit circle, trigonometric functions, graphs, identities and triangle solving. Each topic comes with practice problems and full solutions, perfect before an exam.

Governors State University

A short, friendly introduction that starts with right triangles and solving triangles, then moves on to graphs, identities, equations and the laws of sines and cosines. Ideal for a first course or a quick refresher.

Richard W. Beveridge

A classic school textbook that introduces trigonometry step by step, from measuring angles to ratios, identities, logarithms and solving triangles. Its many worked examples and exercises make it a great first book.

J. B. Lock

Compact course notes that cover radian measure, the six trigonometric ratios, exact values, key identities, inverse functions and trigonometric equations. They end with tutorial exercises for engineering and science students.

Glasgow Caledonian University

A brief introduction to the basics: degrees and radians, the unit circle, the six trigonometric functions and the double-angle formula. A quick read to review the essentials before a calculus course.

P. Maidorn