Question

1+e^-jw+e^-2jw = e^-jw(1+ 2 cos w) ? how ?

Answer 1

$1+e^{-jw}+e^{-2jw}=e^{-jw}[e^{jw} + 1 + e^{-jw} ]\\\\=e^{-jw}*[cosw+j\ sinw+1+cosw-j*sinw]\\\\=e^{-jw}*[1+2 * cosw]$

Answer 2

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