This is a complex analysis question

Apply Parseval's identity to the function 7n - = 1+z + ... + zn- f (Z) = Z - n Z = 1 to show that 2 2 TT sin(znt) dt = 2an 0 sin(-nt) Hint: f(z) is a polynomial hence a power series (about 0) that is defined everywhere on C. Do the estimation on the unit circle, i.e, compute So If(eit) |2 dt and use Parseval's identity