# The addition formulas

## Video 1: Derivation of “the fourth” addition formula.

## Video 2: Using “the fourth” addition formula: Examples

## Reading Suggestions:

- Carefully note the so-called cofunction identities in the shaded box on page 580. If you think about the translations of graphs, these identities should make sense.
- Study the derivations of the remaining angle-addition formulas/identities startiWord count: 179

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ng at the top of page 581. - The addition formulas for the tangent function look different from the ones you’ve seen already but they have a similar effect: They take a trig function with a sum for an input and turn them into an expression only involving single inputs (no sum) to the tangent function. The examples in the text (ex 6 and 7) are similar to those covered in video 2.

## Assignment 8.1

- Part A; p.584: # 1,2,11,13,21,23
- PartB; p.584: #49,55,57

# 8.2 The Double Angle and Half Angle formulas

## Video 3: Double angle formulas.

## Video 4: Half angle formulas.

## Assignment 8.2

- p.595: # 3,5,7,13,17,25,29,34,35

# 8.3 The Product to Sum and the Sum to Product Formulas.

Coming soon: Explanation of example 5, p.602.

## Assignment 8.3

- p.603: 1,7,23,25,35,37
- Honors; p.604: 42,43

# 8.4 Trigonometric equations

## Assignment 8.4

- optional practice: p.616; #1,3
- p. 616; 5,9,11,13,15,25,27,29

## Assignment 8.5

- p. 630, 1-5 odd, 11-19 odd, 25-29 odd