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Trigonometry For Dummies, 2nd Edition by Mary Jane Sterling

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Chapter 11

Identifying Basic Identities

In This Chapter

arrow Recognizing reciprocal identities

arrow Putting functions head-over-tails by using ratio identities

arrow Performing attitude adjustments on negative angles

arrow Relating functions to Pythagoras's way of thinking

arrow Using multiple identities to simplify matters

I'm sure a thousand questions are running through your mind: What's a trig identity? Is it possible to have a mistaken trig identity? Does anyone commit trig-identity theft? Can you have an identity crisis with trig? The answer: No — probably not.

Trig identities aren't nearly as sinister as you may think. They're actually very helpful tools in simplifying trig expressions and solving equations. These identities are special to trigonometry. Basically, they're equivalences — they give you options to substitute into equations in order to simplify. For example, wouldn't you rather use the number 1 than ? Of course! In most cases, the number 1 is simpler. That's how trig identities work — replace ...

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