Let \(X\) be a topological space. A subset \(A\subseteq X\) is an \(F_\sigma\) set if \(A\) is a countable union of closed subsets of \(X\).
What is an $F_\sigma$ set?
$F_\sigma$ sets
FD-BBR6Q
FD-BBR6Q
Let \(X\) be a topological space. A subset \(A\subseteq X\) is an \(F_\sigma\) set if \(A\) is a countable union of closed subsets of \(X\).