\begin{definition}[Definition:Filtering Function/2 Dimensional]
Let $\operatorname {sinc}: \R \to \R$ denote the '''filtering function'''.
The $2$-dimensional form of $\operatorname {sinc}$ is defined and denoted:
:$\forall x, y \in \R: \map {\operatorname { {}^2 sinc} } {x, y} := \map {\operatorname {sinc} } x \map {\operatorname {sinc} } y$
\end{definition}