Mo logo [home] [lexicon] [problems] [tests] [courses] [auxiliaries] [notes] [staff] german flag

Mathematics-Online lexicon:

Division of Complex Numbers


A B C D E F G H I J K L M N O P Q R S T U V W X Y Z overview

The quotient $ z_1/z_2$ of two complex numbers

$\displaystyle z_k = x_k + \mathrm{i} y_k = r_k \exp(\mathrm{i}\varphi_k)
$

is

$\displaystyle \frac{x_1x_2+y_1y_2}{x_2^2+y_2^2} +
\frac{x_2y_1-x_1y_2}{x_2^2+y_2^2}\,\mathrm{i} =
\frac{r_1}{r_2}\exp(\mathrm{i}(\varphi_1-\varphi_2))\,
.
$

In particular,

$\displaystyle \frac{1}{z} =
\frac{1}{r^2} \bar z =
\frac{1}{r} \exp(-\mathrm{i}\varphi) =
\frac{x}{r^2} - \frac{y}{r^2}\,\mathrm{i}
\,.
$

A complex number's reciprocal can be constructed via reflection at the unit circle $ C$, as is illustrated in the following figure.

\includegraphics[height=6cm]{a_division_bild}

The complex conjugate $ w = \bar z$ is the intersection of the diagonals of the quadrilateral formed by the tangents at $ C$ passing through $ z$ and the perpendicular radii. The number $ z$ is then obtained by reflection at the real axis.

(Authors: Höllig/Kopf/Abele)

see also:


[Annotations] [Examples]

  automatically generated 5/ 5/2011