Massachusetts Institute of Technology
Mit: Useful Trigonometric Identities
This list of trigonometric identities includes the factoring formulas near the bottom. A great tool for reference.
Varsity Tutors
Varsity Tutors: Hotmath: Practice Problems: Fundamental Trigonometric Identities
Twenty problems present a variety of practice working with fundamental trigonometric identities. They are given with each step to the solution cleverly revealed one at a time. You can work each step of the problem then click the "View...
Mathematics Archives
Math Archives: Visual Calculus: 47 Trig Identities!
This makes for a great handout for learners and teachers, alike! A comprehensive list of 47 commonly-used trig identities.
Wolfram Research
Wolfram Math World: Inverse Trigonometric Functions
A site on inverse trigonometric functions. Contains a definition, a chart showing functions and their domains, formulas, and many links.
Other
Brown Math: Remembering Trig Identities
Faced with a large number of trigonometric identities, students tend to try to memorize them all. This site the emphasis is on understanding how the functions work and on memorizing only about a half dozen of them - all the others work...
Clark University
Clark University: Dave's Short Trig Course
This Clark University trigonometry tutorial site features questions and answers about what students can learn from trigonometry.
Wolfram Research
Wolfram Math World: Double Angle Formulas
Part of Eric Weisstein's comprehensive math site, this page deals with double-angle formulas. This site includes traditional trigonomic double-angle functions as well as hyperbolic trigonometric function. Includes links to related terms...
Wolfram Research
Wolfram Math World: Half Angle Formulas
This page, from Eric Weisstein's comprehensive Math World site, offers information on half-angle formulas. The site includes traditional trigonometric fuctions half-angle formulas as well as hyperbolic half-angle formulas. Includes links...
Math Words
Math words.com: Trig Identities
This MathWords.com site lists the equations for all of the trigonometric identities.
Math2
Math2.org: Trigonometry Functions
A complete look at trig functions. From an "overview," page giving general definitions and important vocab words, to a listing of the 12 trig functions, to an explanation of the three modes used in trigonometry, to the procedures of how...
Other
Technical Tutoring: The Very Fast Trig Review
This resource is a quick review of the functions and identities in trigonometry.
Other
Technical Tutoring: Trigonometry: The Very Fast Review
This site is a quick review of the functions and identities in trigonometry. Very helpful site.