# Combination Theorem for Continuous Mappings/Normed Division Ring/Negation Rule

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## Theorem

Let $\struct{S, \tau_{_S}}$ be a topological space.

Let $\struct{R, +, *, \norm{\,\cdot\,}}$ be a normed division ring.

Let $\tau_{_R}$ be the topology induced by the norm $\norm{\,\cdot\,}$.

Let $g : \struct{S, \tau_{_S}} \to \struct{R, \tau_{_R}}$ be a continuous mapping.

Let $- g : S \to R$ be the mapping defined by:

- $\forall x \in S: \map {\paren{- g}} x = - \map g x$

Then

- $- g : \struct{S, \tau_{_S}} \to \struct{R, \tau_{_R}}$ is continuous.

## Proof

From Corollary to Normed Division Ring Operations are Continuous, $\struct{R, +, *, \tau_{_R}}$ is a topological division ring.

From Negation Rule for Continuous Mappings to Topological Division Ring, $- g : \struct{S, \tau_{_S}} \to \struct{R, \tau_{_R}}$ is a continuous mapping.

$\blacksquare$