1. Lesson 5.1 Using Trig Identities

2. The textbook calls the following the Fundamental Trig Identities They are down the left side of your “Trig Cheat Sheet” You will want to memorize as many as you can. Recognizing them within an equation will become important.

3. Cofunction Identities These derive from a right triangle With one angle 90 0 the other 2 angles must be complementary Labeling the sides and setting up the 6 trig functions will show you the cofunction identities. u 90 0 - u a b c

4. Cofunction Identities Use the Unit Circle and ask the question: “Would the value change if I plugged in the opposite value”

5. Biggest challenge is to know what to use when!

6. Example Verify the following:

7. Example Rewrite so it is not a fraction:

8. Example Verify the following: Problem Set 5.1