Let $X$ be a compact Hausdorff space, prove $X$ is of second category.
I found a proof of this theorem in the case of locally compact Hausdorff spaces.
Let $E_n$ be open and dense in $X$, locally compact and Hausdorff. Let $$D= \bigcap_{i=1}^{\infty} E_i$$ We must show that $D$ is dense, as this will imply that $X$ is of second category.
Let $U$ be a non-empty open subset of $X$. For $D$ to dense we must have that $U$ intersects $D$. Now $U \cap E_1$ is open, and thus there exists open set $V_1$ such that $\operatorname{cl}(V_1) \subset U \cap E_1$, by Hausdorff and local compactness.
I know that there exists an open set $V_1 \subset U \cap E_1$, since intersection of $U$ and $E_1$ is open and $E_1$ is dense. However, Why does local compactness and Hausdorff imply that closure of such a set will be a subset?
$X$ is a locally compact Hausdorff space, so every point has a local base of open nbhds with compact closures. Suppose that $x\in X$ and $U$ is an open nbhd of $x$. Then there is an open $B$ such that $x\in B\subseteq U$, and $\operatorname{cl}B$ is compact. But then $\operatorname{cl}B$ is a compact Hausdorff space and therefore regular, so there is an open nbhd $V$ of $x$ such that $\operatorname{cl}V\subseteq B\subseteq U$.