I am self-studying analysis and ran across this:
$\mathbb R \setminus \mathbb N$ is an open subset of $\mathbb R$
My best guess for interpretation was this:
the set $\mathbb R \setminus \mathbb N$ is an open subset of $\mathbb R$.
which doesn't mean much to me. Can anyone clear this up a bit? I know that the 'divided by' symbol is usually a slash in the opposite direction. And I am unsure how I would divide the reals by the naturals anyway.