Lesson 13: Using Sum And Difference Formulas For Sine And Cosine


Lesson on using the sum and difference formulas on the trigonometric functions. When not presented with special angles, it would be hard to use the special trigonometric values such as sin30 degrees. However, certain angles are made up of special angles when addition or subtraction operations are performed. The sum and differences can be used in proving trigonometric statements, and can be used to evaluate trigonometric expressions. 

0;54 Find the exact value of cos75 degrees.
5:12 Find the exact value of sin pi/12
6:51 Find the exact value of (sin42)(cos12) -- (cos42)(sin12)
8:19 Find all the solutions of sin (x+ pi/4) + sin (x -- pi/4) = 1

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Part 2: Sum and Difference Formula