froom my textbook it writes:
de moivre's thm
for
i don't understand why k cannot be greater than q-1. thanks
it can be, just if you do the solution you get will be exactly the same as one you have found before say for example if k=q
we have
this is identical to which is the result with k=0
(because sine and cosine are periodic functions with period 2pi)
so k could be q,q+1...etc just you would just repeat all of the solutions