The Countable Union of Countable Sets

We prove that an infinite subset of a countable set is countable. We also prove that the countable union of countable sets in countable.
#mikedabkowski, #mikethemathematician, #profdabkowski, #realanalysis

[@SSCHeroes796]

Excellent❤

[@mikethemathematician]

@SSCHeroes796 Thanks so much! I love Real Analysis!