Hello, kelsey3!
We need this double-angle identity: .
And this sum-to-product identity: .
Verify the identity: .
The right side is: .
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Verify the identity: 2cos4xsin2x=2sin3xcos3x-2cosxsinx.
I know I have to use the product to sum identities but im still stuck.
So far I have, sin(3x+3x)+sin(3x-3x)-sin(x+x)-sin(x-x)
What happens to the sin after you subtract 3x-3x and x-x?