1. Ch 5.4: Sum and Difference Formulas

2. Here is the trigonometry sum and difference formulas introduced in an interesting way:

3. Learn these!!

4. How do we use this? Finding exact values of trig expressions 1.Split the given number into the sum/difference of unit circle values we know 2.Change the problem using the correct formula 3.Simplify by replacing in trig values

5. Examples: Find the exact values 1. Split 75 o into 30 o and 45 o since 2. Use the cosine formula 3. Replace with Trig values

6. Examples: Find the exact values 1. Look at your formulas. Which one does it match? 2. What is u and v? 3. Plug in to the left- hand side and simplify, if possible 4.

7. Find cos(u-v) if and 1. Look at your cosine formula. You need to know sinv and cosu 2. Draw the triangles for each given function 3. Find the missing sides 4. Find sinv and cosu 5. Put it all in your formula!

8. Prove: 1. Just like Ch 5.2, turn the left side into the right side using the difference formula 2. 3. Plug in and simplify!