Isometric Metric Spaces are Homeomorphic

Theorem
Let $M_1 = \left({A_1, d_1}\right)$ and $M_2 = \left({A_2, d_2}\right)$ be metric spaces.

Let $M_1$ and $M_2$ be isometric.

Then $M_1$ and $M_2$ are homeomorphic.

Proof
By the definition of an isometry, there exists a bijection $f: A_1 \to A_2$ such that:
 * $\forall a, b \in A_1: d_1 \left({a, b}\right) = d_2 \left({\phi \left({a}\right), \phi \left({b}\right)}\right)$

From Isometry of Metric Spaces is Homeomorphism, $f$ is a homeomorphism from $M_1$ to $M_2$.

The result follows by definition of homeomorphic metric spaces.