Let $X_j$ be a
D11: Set for each $j \in J$ such that
(i) |
$\bigcup_{j \in J} X_j$ is the D77: Set union of $X = \{ X_j \}_{j \in J}$
|
The
cartesian product of $X = \{ X_j \}_{j \in J}$ is the
D11: Set
\begin{equation}
\prod_{j \in J} X_j
: = \left\{ x : J \to \bigcup_{j \in J} X_j \mid \forall \, j \in J : x_j \in X_j \right\}
\end{equation}