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. a)sin(390°+120°) b)sin390° + sin120°

Sum and Difference Formulas

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

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

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.

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

Using Sum/Diff to Verify Verify the identity sin(x + y)sin(x – y) = sin 2 x – sin 2 y

You Try! Verify each identity 1)sin(3π - x) = sinx 2)cos(x + y) + cos(x - y) = 2cosxcosy 3) Solve for x in the interval [0, 2π) 4) 5)