Asked by kaitlyn

Help please!
sin4x=3cos^3xsinx-4sin^3xcosx
Answered by katelyn
I'm not sure if this is a half angle identity because the cubes throw me off
Answered by Reiny
simplify the left side into x's
sin 4x
= 2sin 2x cos 2x
= 4sinx cosx(cos^2x - sin^2x)
= 4cos^3 x sinx - 4sin^2 x cosx

= almost the right side

I suspect a typo
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