Chapter 8

# Basic Trig Identities

IN THIS CHAPTER

Simplifying with reciprocal, Pythagorean, and co-function identities

Finding patterns with even-odd identities

Discovering periodicity identities

Tackling trigonometric proofs

Ever want to pretend you were someone else — change your identity? Well, trig expressions have the opportunity to do that all the time. In this chapter, you discover basic identities, or statements that are always true. These identities are used to simplify problems and then to complete trigonometric proofs. Each section builds upon the previous one, so you may want to spend some time reviewing the identities in each section before jumping to the end, to practice proofs.

## Using Reciprocal Identities to Simplify Trig Expressions

You actually may have seen some trigonometry expressions back in Chapter 6. In this chapter, you use reciprocal identities to simplify more complicated trig expressions. Because these identities are basically all review, you also find the ratios of tangent and cotangent — the ratio identities that are introduced in Chapter 6. The reciprocal ...

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