Definition:Complex Disk/Open

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Definition

Let $a \in \C$ be a complex number.

Let $R > 0$ be a real number.

The open (complex) disk of center $a$ and radius $R$ is the set:

$\map B {a, R} = \set {z \in \C: \cmod {z - a} < R}$

where $\cmod {\, \cdot \,}$ denotes complex modulus.

Also see

• Definition:Closed Complex Disk