Product Space is T3 iff Factor Spaces are T3/Product Space is T3 implies Factor Spaces are T3

Theorem
Let $\mathbb S = \family {\struct {S_\alpha, \tau_\alpha} }_{\alpha \mathop \in I}$ be an indexed family of non-empty topological spaces for $\alpha$ in some indexing set $I$.

Let $\ds T = \struct{S, \tau} = \prod_{\alpha \mathop \in I} \struct {S_\alpha, \tau_\alpha}$ be the product space of $\mathbb S$.

Let $T$ be a $T_3$ space.

Then for each $\alpha \in I$, $\struct {S_\alpha, \tau_\alpha}$ is a $T_3$ space.

Proof
Suppose $T$ is a $T_3$ space.

As $S_\alpha \ne \O$ we also have $S \ne \O$ by the axiom of choice.

Let $\alpha \in I$.

From Subspace of Product Space is Homeomorphic to Factor Space, $\struct {S_\alpha, \tau_\alpha}$ is homeomorphic to a subspace $T_\alpha$ of $T$.

From $T_3$ property is hereditary, $T_\alpha$ is $T_3$.

From T3 Space is Preserved under Homeomorphism, $\struct {S_\alpha, \tau_\alpha}$ is $T_3$.

As $\alpha \in I$ was arbitrary, the result follows.