# Mapping Induced on Power Set by Inverse Relation is Mapping

## Theorem

Let $\mathcal R \subseteq S \times T$ be a relation on $S \times T$.

Let $\mathcal R^\gets$ be the mapping induced on the power set of $S$ by the inverse relation $\mathcal R^{-1}$:

$\mathcal R^\gets: \mathcal P \left({T}\right) \to \mathcal P \left({S}\right): \mathcal R^\gets \left({Y}\right) = \mathcal R^{-1} \left[{Y}\right]$

Then $\mathcal R^\gets$ is indeed a mapping.

## Proof

$\mathcal R^{-1}$, being a relation, obeys the same laws as $\mathcal R$.

So Mapping Induced on Power Set is Mapping applies directly.

$\blacksquare$