Trig identity

1. thenewbosco

187
no clue how to start this:

show

sin 3x = 3 sin x - 4 sin^3 x

2. Dr Avalanchez

18
How to start this: sin(3x) = sin(2x+x)

3. thenewbosco

187
right so after doing this i get

sin 3x = sin2x(cos x) + (cos2x)(sin x)

whats next

18
sin(2x)=...?
cos(2x)=...?

5. thenewbosco

187
thanks for the help i got this and the others