1. Sum and Difference Formulas
Skill 34

2. Objectives…
Use sum and difference formulas to evaluate trigonometric functions, verify trigonometric identities, and solve trigonometric equations.

4. Example– Evaluating a Trigonometric Function
Find the exact value of (a) cos 75 ° and (b) sin .
Solution:
a cos 75 ° = cos(30 ° + 45 °)
= cos 30  cos 45  – sin 30  sin 45 

5. Example–Solution
b. sin (u – v)

6. Example– An Application of a Sum Formula
Write as an algebraic expression

7. Example– Reduction Formula

8. Example– Reduction Formula

9. Example– An Application of a Sum Formula

10. Example– Solving Trigonometric Equations #84

11. Example– Solving Trigonometric Equations #84
Not in domain

12. Example– Verify the Trigonometric Equation

13. 34 Sum & Difference Formulas
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