Inversion Mapping on Topological Group is Homeomorphism

Theorem
Let $T = \left({G, \circ, \tau}\right)$ be a topological group.

Let $\phi: G \to G$ be the inversion mapping of $T$.

Then $\phi$ is a homeomorphism.

Proof
From the definition of topological group, $\phi$ is continuous.

By Inversion Mapping is Involution, $\phi$ is an involution.

Thus by Continuous Involution is Homeomorphism, $\phi$ is a homeomorphism.