Cho dãy X ( k ) = 2 1 − c o s k − j s i n k , hãy xác dịnh phần thực và phần ảo

$\text{R}\text{e}\left[X\left(k\right)\right]=\frac{2-2\text{c}\text{o}\text{s}k}{1-\text{c}\text{o}\text{s}k-j\text{s}\text{i}\text{n}k},\text{I}\text{m}\left[X\left(k\right)\right]=\frac{j\text{s}\text{i}\text{n}k}{1-\text{c}\text{o}\text{s}k-j\text{s}\text{i}\text{n}k}$

$\text{R}\text{e}\left[X\left(k\right)\right]=\frac{2}{1-\text{c}\text{o}\text{s}k},\text{I}\text{m}\left[X\left(k\right)\right]=\frac{-2}{\text{s}\text{i}\text{n}k}$

$\text{R}\text{e}\left[X\left(k\right)\right]=\frac{\text{c}\text{o}\text{s}k}{1-\text{c}\text{o}\text{s}k},\text{I}\text{m}\left[X\left(k\right)\right]=\frac{\text{s}\text{i}\text{n}k}{1-\text{c}\text{o}\text{s}k}$

$\text{R}\text{e}\left[X\left(k\right)\right]=1,\text{I}\text{m}\left[X\left(k\right)\right]=\frac{\text{s}\text{i}\text{n}k}{1-\text{c}\text{o}\text{s}k}$.