\begin{definition}[Definition:Continuous Complex Function/Open Sets]
Let $A_1, A_2 \subseteq \C$ be subsets of the complex plane.
Let $f: A_1 \to A_2$ be a complex function from $A_1$ to $A_2$.
$f$ is '''continuous''' {{iff}}:
:for every set $U \subseteq \C$ which is open in $\C$, $\map {f^{-1} } U$ is open in $\C$.
Category:Definitions/Complex Analysis
\end{definition}