dft windowing

I have been using excel to calculate the power spectrums for both HANN and RECTANGULAR windowing with : N - 1 DFT = X(K) =1/N ∑ x(n) ( cos (2πnk/N) - j sin (2πnk/N) ) n = 0 HANN x(n) = 0.5 (1 - cos (2πn/(N-1)))...