2/26/08
Discrete time fourier series
x[n] = sum<r=<No>>(Dre^(jrOMEGAn))	x[n] must be No periodic
Dr=(1/No)*sum<n=<No>>(x[n]e^(-jrOMEGAn))

ex
x[n] = cos(n*pi/10) -> OMEGA = pi/10 -> No = m2pi/OMEGA = m20 -> No=20
x[n] = sum<r=<20>>(Dre^(jpirn/10))
Dr = (1/20)*sum<n=<20>>(x[n]e^(-jrnpi/10)) = (1/40)sum<n=<20>>(e^((1-r)jpin/10)+e^((r+1)(-jpin/10)))
D1 = (geometric series) -> = 1/2

example (Fig1)
example (Fig2)