1. Sum & Difference Formulas
Objective: Be able to use sum & difference formulas to find trig functions of non-unit circle values, simplify, verify, solve, etc, etc.
TS: Explicitly assess information and draw conclusions
Warm-Up: Find the exact value of each.
sin(390°+120°)
sin390° + sin120°

2. Sum and Difference Formulas

3. Using Sum/Diff to Find Exact Values
Find the sine for 285°, using the fact 285°=330° – 45°

4. Using Sum/Diff to Find Exact Values
Find the cosine for

5. Using Sum/Diff to Find Exact Values
Find tan(u+v) where sin(u) = -7/25 & cos(v) = -4/5. Both u & v are in quadrant III.

6. Using Sum/Diff to Simplify
Write the expression as the sine, cosine or tangent of an angle.
cos(0.88)cos(0.34)+sin(0.88)sin(0.34) b)

7. Using Sum/Diff to Verify
Verify the identity
sin(x + y)sin(x – y) = sin2x – sin2y

8. You Try! Verify each identity sin(3π - x) = sinx
cos(x + y) + cos(x - y) = 2cosxcosy 3)
Solve for x in the interval [0, 2π) 4) 5)