Editing Z-transform (section)

=== Bilateral Z-transform ===
The ''bilateral'' or ''two-sided'' Z-transform of a discrete-time signal <math>x[n]</math> is the [[formal power series]] <math>X(z)</math> defined as:

{{Equation box 1 |title=
|indent =: |cellpadding= 6 |border |border colour = #0073CF |background colour=#F5FFFA
|equation = <math>X(z) = \mathcal{Z}\{x[n]\} = \sum_{n=-\infty}^{\infty} x[n] z^{-n}</math>
}}

where <math>n</math> is an integer and <math>z</math> is, in general, a [[complex number]]. In [[Polar coordinate system#Complex numbers|polar form]], <math>z</math> may be written as:
:<math>z = A e^{j\phi} = A\cdot(\cos{\phi}+j\sin{\phi})</math>
where <math>A</math> is the magnitude of <math>z</math>, <math>j</math> is the [[imaginary unit]], and <math>\phi</math> is the ''[[complex argument]]'' (also referred to as ''angle'' or ''phase'') in [[radian]]s.