Question

How do I expand 4cos(6x) in terms of sines using the double angle identity?

Answer 1

Your attempt?

Answer 2

Hint 6x = 2(3x)

Answer 3

\(cos 2(x) = 1- 2sin^2 (x)\)
now you have \(cos 2(3x) = 1-2sin^2(3x)\) , got me so far??

Answer 4

Yes.

Answer 5

so?? just times4 in the front both sides, you get what you want to get.
\(\color {red}{4}cos (6x)= \color{red}{4}*....\) can you finish??

Answer 6

Yeah. Totally. That was way simpler than I was trying to make it be.

Answer 7

Thank you so much.

Answer 8

hahahahaa

Answer 9

I was breaking it into cos(3x+3x) and using that identity and it was a total mess. Thank you.

Answer 10

ok