Hãy xác định giá trị module và argument của X ( e j ϖ ) biết. x ( n ) = r e c t ℕ ( n − 1 )

$\left|X\left(e{}^{j\omega }\right)\right|=\left|\text{s}\text{i}\text{n}\omega \frac{N-n{}_0-1}{2}\right|$$\text{a}\text{r}\text{g}\left[X\left(e{}^{j\omega }\right)\right]=-\text{a}\text{r}\text{c}\text{t}\text{g}\frac{\text{s}\text{i}\text{n}\omega \frac{N-1}{2}}{1+\text{c}\text{o}\text{s}\omega \frac{N-1}{2}}$

$\left|X\left(e{}^{j\omega }\right)\right|=\left|\frac{\text{s}\text{i}\text{n}\omega N}{\text{s}\text{i}\text{n}\omega }\right|$$\text{a}\text{r}\text{g}X\left(e{}^{j\omega }\right)=\omega \left(N-1\right)$

$\left|X\left(e{}^{j\omega }\right)\right|=\left|\frac{\text{s}\text{i}\text{n}\omega N}{\text{s}\text{i}\text{n}\omega }\right|$$\text{a}\text{r}\text{g}\left[X\left(e{}^{j\omega }\right)\right]=\text{a}\text{r}\text{g}\left[\frac{\text{s}\text{i}\text{n}\omega N}{\text{s}\text{i}\text{n}\omega }\right]+\omega \left(N-1\right)$

$\left|X\left(e{}^{j\omega }\right)\right|=\left|\frac{\text{s}\text{i}\text{n}\frac{\omega N}{2}}{\text{s}\text{i}\text{n}\frac{\omega }{2}}\right|$$\text{a}\text{r}\text{g}\left[X\left(e{}^{j\omega }\right)\right]=\text{a}\text{r}\text{g}\left[\frac{\text{s}\text{i}\text{n}\frac{\omega N}{2}}{\text{s}\text{i}\text{n}\frac{\omega }{2}}\right]-\omega \left(\frac{N+1}{2}\right)$