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

Set cardinality in terms of finite ambient set

Formulation 0

Let $X$ be a D17: Finite set such that

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

Then \begin{equation} |E| = |X| - |X \setminus E| \end{equation}

Proofs

Proof 0

Let $X$ be a D17: Finite set such that

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

This result is a particular case of R4189: . $\square$