Trigonometry For Dummies, 2nd Edition

Chapter 13

Proving Identities: The Basics

In This Chapter

Brushing up on the major identities

Working on one or both sides

Changing everything to sine and cosine

Dealing with fractions

One major aspect that people remember about trigonometry, if they studied it in school, is the time they spent proving identities — making one side of an equation match the other. Some people find proving identities to be the best thing ever — they can't get enough of them. Others, though, find this task of proving identities to be less than exciting — a rite of passage that is best passed by. What you find in this chapter are a game plan and suggestions so those who aren't so fond of solving such puzzles so they may begin to actually enjoy the process. For your reading pleasure, I divide this chapter into the methods that work best to prove the different types of identities.

Why do you need to prove identities? Don't you already know that they're correct if they're called identities? Sure you do, but proving them is still helpful down the road when you're solving complex trig problems, because the ...