Question

show that 4sinθsin(π/3+θ) sin(2π/3 +θ)=sin3θ

Answer 1

Do you know how to expand sin(a+b)?

Answer 2

yes

Answer 3

If you expand the two sin(__+__) parts, you should be able to get a recognizable form.

Answer 4

i dont know what do you mean :(

Answer 5

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.