if you already have the answer, why post the question?
Just use your sum-of-angles formulas if you need the steps. Post your work if you get stuck.
When you get to the point where you have
sin(10°-x)sin(20°+x) - cos(10°-x)cos(20°+x)
use your product-to-sum formulas
sin(350°+θ)cos(110°+θ)-cos(350°+θ)sin(110°+θ)=
Ans: −√3/2
1 answer