Question

By writing sin3x as sin(x+2x)
Show that sin3x=3sinx=4sin^3x

Answer 1

??

Answer 2

that ain't right

Answer 3

It is written like that
I'm assuming they mean sin3x=sin3x-4sin^3x
But I don't really understand it

Answer 4

oops sorry
it is supposed to be 3sinx-4sin^3x
sorry about that

Answer 5

\[\sin3x = 3sinx -4\sin^3x\]
Use: \(\sin(2x+x)\) to prove it.

Answer 6

I just don't know how to start it with sin(2x+x)

Answer 7

Well, expand it first using the formula sin(a+b)
\[\sin2xcosx + \cos2xsinx\]

Answer 8

oh! How dumb of me :(
I got it from here, totally forgot about that.

Answer 9

ok, do you need more help? on how to continue it?

Answer 10

I believe I can figure this question out from here.
Thank you so much for jogging my memory!

Answer 11

yw (: