Express cos^(4)2x in terms of cosine with an exponent of 1?
Hi, this is my first time using this site.
So I have been staring at this trigonometric equation for a long while and looking for what it asks for. For what I know, I think I have to use sum of difference identities, but I am not so sure where to begin from there. I know I am working for an answer of cosine, but then I am lost as to what identity I should use, or if I am using the right identity.
I really appreciate any help for this problem and I thank you.