1. Product-to-Sum and Sum-to-Product Formulas

2. Product-to-Sum Formulas
Changing an equation from a multiplication problem to an addition problem

3. Expressing Products as Sums
Express each of the following products as a sum containing only sines or cosines.
(a) sin (6q) sin (4q)
(b) cos (3q) cos (q)

4. Expressing Products as Sums
(c) sin (3q) cos (5q)

5. Sum-to-Product Formulas
Changing equations from an addition problem to a multiplication problem

6. Expressing Sums as a Product
Express each sum or difference as a product of sines and/or cosines.
(a) sin (5q) – sin (3q)
(b) sin (4q) + sin (2q)

7. Expressing Sums as Products
(c) cos q – cos (3q)
(d) cos (5q) + cos (3q)

8. Establishing Identities
Establish the identity

9. Establishing Identities
Establish the identity

10. Product-to-Sum and Sum-to-Product
On-line Tutorial
On-line Video