1. Sum and Difference Identities
Demana, Waits, Foley, Kennedy
5.3
Sum and Difference Identities

2. What you’ll learn about
Cosine of a Difference
Cosine of a Sum
Sine of a Difference or Sum
Tangent of a Difference or Sum
Verifying a Sinusoid Algebraically
… and why
These identities provide clear examples of how different
the algebra of functions can be from the algebra of real
numbers.

3. Does the Distributive Law Apply?

4. Cosine of a Sum or Difference

5. Example: Using the Cosine-of-a-Difference Identity

6. Solution

7. Sine of a Sum or Difference

8. Example: Using the Sum and Difference Formulas

9. Solution

10. Prove the Cofunction Identities

11. Tangent of a Difference of Sum
Why would we need two different versions for the same thing ?

12. Show that

13. Example: Expressing a Sum of Sinusoids as a Sinusoid

14. Solution

15. Solution

16. Solution

17. Solution

18. Solution