This document discusses trigonometric identities related to the difference of squares formula and provides examples of using identities to simplify expressions involving sine, cosine, secant, and tangent functions. It also assigns worksheet problems involving using these trigonometric identities.

1. Difference of Squares
(a + b)(a - b)
= 1 - sin
= (1 - sin )(1 + sin )
Likewise:
= 1 - cos
= sec + tan
1 - sin

2. 1 - cos
1 + cos
- 1 = sin
Assignment:
WS Id-Id #13, 14, 19, 20, 39, 43, 44

3. ex. 1 - cos = sin
1 + cos
Id-Id WS #13, 14, 19, 20, 39, 43, 44