SOLUTION: Verify the identity: sin4x=4sinxcosx - 8 sin^3cosx

Algebra ->  Trigonometry-basics -> SOLUTION: Verify the identity: sin4x=4sinxcosx - 8 sin^3cosx       Log On


   

Question 974517: Verify the identity: sin4x=4sinxcosx - 8 sin^3cosx
Answer by FrankM(1040) About Me  (Show Source):
You can put this solution on YOUR website!
For this solution, we're going to use 2 double angle equations:
sin%282x%29=2sin%28x%29cos%28x%29
and
cos%282x%29=1-2sin%5E2%28x%29

sin%284x%29=2sin%282x%29cos%282x%29

2%282sin%28x%29cos%28x%29%29%281-2sin%5E2%28x%29%29

4sin%28x%29cos%28x%29-8sin%5E3%28x%29cos%28x%29
and it looks like this
.