Question

4sinθsin(π/3+θ) sin(2π/3 +θ)=sin3θ

Answer 1

you get 4 sinθ sin(π/3) cosθ sinθ cos(π/3) sin(2π/3) cosθ sinθ cos(2π/3). This simplifies (in a very convoluted manner) to sin(3θ). Basically, evaluate the sin(stuff) that you know. Then, expand sin(3θ). You should be able to see what to do from there.