Combination Theorem for Continuous Mappings/Topological Group/Inverse Rule

Theorem
Let $\struct {S, \tau_S}$ be a topological space.

Let $\struct {G, *, \tau_G}$ be a topological group.

Let $g: \struct {S, \tau_S} \to \struct {G, \tau_G}$ be a continuous mapping.

Let $g^{-1}: S \to G$ be the mapping defined by:
 * $\forall x \in S: \map {\paren {g^{-1} } } x = \paren {\map g x}^{-1}$

Then:
 * $g^{-1}: \struct {S, \tau_S} \to \struct {G, \tau_G}$ is a continuous mapping.

Proof
By definition of a topological group:
 * $\phi: \struct {G, \tau_G} \to \struct {G, \tau_G}$ such that $\forall x \in G: \map \phi x = x^{-1}$ is a continuous mapping

From Composite of Continuous Mappings is Continuous:
 * the composition $\phi \circ g: \struct {S, \tau_S} \to \struct {G, \tau_G}$ is continuous.

Now:

From Equality of Mappings:
 * $g^{-1} = \phi \circ g$

The result follows.