Sum and Difference Trigonometric Identities

Using the Sum and Difference Identities, I do examples of evaluating trigonometric expressions that require the use of the sum and difference identities for sine, cosine, and tangent. At the end of the example of sin(195) (at 8:04) I say the denominator of the answer is 2 but 2*2 equals 4. Sorry for the error. There is an annotation correction, but you will not see it if you do not have Flash. Check out http://www.ProfRobBob.com/, there you will find my lessons organized by class/subject and then by topics within each class. Find free review test, useful notes and more at http://www.mathplane.com/ If you'd like to make a donation to support my efforts look for the "Tip the Teacher" button on my channel's homepage    / profrobbob