Theorem
If the class of real valued continuous functions separates points of a space then that space is hausdorff.
Theorem
Letbe distinct points of
and let
be the class of real valued continuous functions on
Since
separates points, a continuous function
exists such that
There are open disjoint subsetsand
such that
Sinceis continuous
and
are open and disjoint with
and
Henceis a Hausdorff or T2 space.