sorry - that is not true.
It is clearly false for x = π/4
The parentheses balance, but it makes no sense.
It is true for x = kπ but that does not make it an identity.
Prove 8sin^5x=sinx(3-4cos(2x)+cos(4x))
2 answers
I just need to try to manipulate one side of the equation to equal the other side. That's what I mean by prove.