Separable Metric Space is Homeomorphic to Subspace of Fréchet Metric Space

Theorem
Let $M = \struct {A, d}$ be a metric space whose induced topology is separable.

Then $M$ is homeomorphic to a subspace of the Fréchet space $\struct {\R^\omega, d}$ on the countable-dimensional real Cartesian space $\R^\omega$.

Proof
Let $f: M \to \R^\omega$ be the mapping defined as:
 * $\forall x \in M: \map f x = \sequence {\map d {x, x_i} }$

where $\set {x_i}$ is a countable dense subset of $A$.

It remains to be shown that $f$ is a homeomorphism.