ThmDex – An index of mathematical definitions, results, and conjectures.

Result R977 on D77: Set union

Ambient set is union of subset and complement of subset

Formulation 0

Let $X$ be a D11: Set such that

(i)	$E \subseteq X$ is a D78: Subset of $X$

Then \begin{equation} X = E \cup (X \setminus E) \end{equation}