I need help using the complex exponential to express
cos6x as a polynomial in terms of cosx
I don't know how to get it in terms of cosx without sinx.
where the expansion is done using the binomial theorem
and I'll leave the expansion and subsequent simplification for you.
I get ......
You should check that your answer gives 1 when you substitute x = 0. (Or that you get -1 when you substitute )
ps: I reserve the right for at least one error in this reply.