Trig

These pages are pretty good for finding the identity and an explanation

http://www.themathpage.com/atrig/trigonometric-identities.htm

http://www.sosmath.com/trig/Trig5/trig5/trig5.html

http://tutorial.math.lamar.edu/pdf/Trig_Cheat_Sheet_Reduced.pdf

^^^^^this one has the unit circle as well as the law of sines and cosines

http://www.teicontrols.com/notes/Trigonometry/Identities.pdf

^^^^^^ this one briefly touches the hyperbolic identites and mclaurin expansions and has a trig chart for common angles. if you have questions about hyperbolic trig make a thread. this one also touches the complex numbers