Xác định x ( n ) biết X ( e j ω ) = e − j ω với − π ≤ ω ≤ π

$x\left(n\right)=\frac{\text{c}\text{o}\text{s}\pi \left(n-1\right)}{\pi \left(n-1\right)}$

$\text{x}\left(\text{n}\right)=\frac{\text{c}\text{o}\text{s}\omega \left(n-1\right)}{\pi \left(n-1\right)}$

$\text{x}\left(\text{n}\right)=\frac{\text{s}\text{i}\text{n}\pi n}{\pi n}$

$\text{x}\left(\text{n}\right)=\frac{\text{s}\text{i}\text{n}\pi \left(n-1\right)}{\pi \left(n-1\right)}=\delta \left(\text{n}-1\right)$