A countable union of countable sets is countable

In this video, we are going to discuss the basic result in set theory that a countable union of countable sets is countable. If you like the video, please help my channel grow by subscribing to my channel and sharing my videos. Thank you for watching! 00:00 - Intro 00:40 - Countable set definition 02:00 - Proof 05:15 - Second statement 06:30 - Counter example Maksym Zubkov zubkovmaksym@gmail.com ~-~~-~~~-~~-~ Please watch: "Real Projective Space, n=1"    • Real Projective Space, n=1   ~-~~-~~~-~~-~