1. Trig Identities
Lesson 3.1

2. Ratio Identities
Since we know that x = cos t and y = cos t …

3. Reciprocal Identities
Identities given by definition

4. Pythagorean Identities
From the unit circle we saw that x2 + y2 = 1
Thus
Also from (x, y) defn.
(x,y) θ
r y x

5. Verifying Trig Identities
We will be given an equation
Must prove that it is an identity
Strategy
Work with one side only
Substitute expressions using the identities
Goal is to manipulate one side to look like the other side

6. Try It Out
Try these

7. Assignment
Lesson 3.1
Page 222
Exercises 1 – 55 EOO