ThmDex – An index of mathematical definitions, results, and conjectures.
Transforming an isotone sequence of sets into pairwise disjoint sequence with common limit
Formulation 1
Let $E_0, E_1, E_2, \ldots$ each be a D11: Set such that
(i) \begin{equation} E_0 \subseteq E_1 \subseteq E_2 \subseteq \cdots \end{equation}
Let $F_0, F_1, F_2, \ldots$ each be a D11: Set such that
(i) \begin{equation} F_0 : = E_0 \end{equation}
(ii) \begin{equation} \forall \, n \in 1, 2, 3, \ldots : F_n : = E_{n + 1} \setminus E_n \end{equation}
Then
(1) \begin{equation} \forall \, n, m \in \mathbb{N} \, (n \neq m \quad \Rightarrow \quad F_n \cap F_m = \emptyset) \end{equation}
(2) \begin{equation} \bigcup_{n \in \mathbb{N}} E_n = \bigcup_{n \in \mathbb{N}} F_n \end{equation}