Would you use De Moivres theorem here and expand it? Not to sure!
By writing sin theta in terms of z = e ^(i theta), express sin^6 theta as a sum of
terms of the form k cos(h theta)
You don't need to write it in terms of .
If , then
Expand this using the Binomial Theorem and write in terms of real and imaginary parts.
You should also know that by DeMoivre's Theorem.
So once you have written the binomial expansion in terms of its real and imaginary parts, you can then equate real and imaginary parts and solve the problem.