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.
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.
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.
Johan Claeys
Math Abundance: Inverse Trigonometric Functions = Cyclometric Functions
Explains the inverse trigonometric functions using examples.
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.