Simplifying Trig Identities

Dr Dendane, Abdelkader "Using the trigonometric identities." Free Mathematics Tutorials, November 26 2007. <http://www.analyzemath.com/Trigonometry_2/Use_trigo_identities.html>

Larson, Ron, and Robert P. Hostetler. Precalculus. New York: Houghton Mifflin Company, 2004.