I agree.
What about it?
Sin3x=3cos^2xsinx-sin^3x
2 answers
If you're trying to prove it,
sin(3x) = sin(2x+x)
= sin2x cosx + cos2x sinx
= 2sinx cos^2 x + (cos^2x-sin^2x)sinx
= 2sinx cos^2x + cos^2x sinx - sin^3x
ta da
sin(3x) = sin(2x+x)
= sin2x cosx + cos2x sinx
= 2sinx cos^2 x + (cos^2x-sin^2x)sinx
= 2sinx cos^2x + cos^2x sinx - sin^3x
ta da