EDB — 03P

Exercises

1. [03P] Prerequisites: [036]↺↻,[03H]↺↻.

   Let \(A_ 0.A_ 1\ldots A_ n\ldots \) sets of countable cardinality, for \(n\in {\mathbb {N}}\).

   Show that \(B=\bigcup _{k=0}^\infty A_ k\) is countable.

   Note that \(B\) is infinite-countable if for example there is at least one \(n\) for which \(A_ n\) is infinite-countable.

   Solution 1

   [03Q]↺↻