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.
Math Medics
S.o.s. Math: Trigonometric Equations
This math lesson presents methods of solving trigonometric equations when the answer does not seem obvious. The lesson begins by giving an example then has a few practice problems for viewers to solve with solutions as links.
Other
All Elementary Mathematics: Trigonometric Equations
This site gives a definition for what a trigonometric equation is, gives a listing of the simplest trigonometric equations, and lists seven main methods of solution of trigonometric equations with examples.
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...
Cool Math
Coolmath: Solving Trig Equations
This CoolMath resource explains how to solve trigonometric equations
Other
Technical Tutoring: Trigonometry: The Very Fast Review
This site is a quick review of the functions and identities in trigonometry. Very helpful site.
Math Medics
S.o.s. Math: Solving Trigonometric Equations
This lesson contains trigonometric equations of various forms that you can solve. The problems contain the answers solved in three different ways: algebraically, graphically, and using the concept of equivalence.