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

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

Result R3507 on D16: Countable set

Binary union of countable sets is countable

Formulation 0

Let $X$ and $Y$ each be a D16: Countable set.

Then $X \cup Y$ is a D16: Countable set.

Proofs

Proof 0

Let $X$ and $Y$ each be a D16: Countable set.

This is a subresult to R3506: Finite union of countable sets is countable. $\square$