Hãy xác định Y ( e j ω ) nếu. F T [ x ( n ) ] = X ( e j ω ) ; F T [ y ( n ) ] = Y ( e j ω ) . Với y ( n ) = n . x

$Y\left(e{}^{j\omega }\right)=\frac{dX\left(e{}^{j\omega }\right)}{d\omega }$

$Y\left(e{}^{j\omega }\right)=e{}^{j\omega }\frac{dX\left(e{}^{j\omega }\right)}{d\omega }$

$Y\left(e{}^{j\omega }\right)=j\frac{dX\left(e{}^{j\omega }\right)}{d\omega }$

$Y\left(e{}^{j\omega }\right)=e{}^{-j\omega }\frac{dX\left(e{}^{j\omega }\right)}{d\omega }$