Category:Definitions/Polar Form of Complex Number

From ProofWiki
Jump to navigation Jump to search

This category contains definitions related to Polar Form of Complex Number.
Related results can be found in Category:Polar Form of Complex Number.


For any complex number $z = x + i y \ne 0$, let:

\(\ds r\) \(=\) \(\ds \cmod z = \sqrt {x^2 + y^2}\) the modulus of $z$, and
\(\ds \theta\) \(=\) \(\ds \arg z\) the argument of $z$ (the angle which $z$ yields with the real line)

where $x, y \in \R$.

From the definition of $\arg z$:

$(1): \quad \dfrac x r = \cos \theta$
$(2): \quad \dfrac y r = \sin \theta$

which implies that:

$x = r \cos \theta$
$y = r \sin \theta$

which in turn means that any number $z = x + i y \ne 0$ can be written as:

$z = x + i y = r \paren {\cos \theta + i \sin \theta}$

The pair $\polar {r, \theta}$ is called the polar form of the complex number $z \ne 0$.


The number $z = 0 + 0 i$ is defined as $\polar {0, 0}$.