Image of Singleton under Relation

Theorem
Let $$\mathcal{R} \subseteq S \times T$$ be a relation.

Then the image of an element of $$S$$ is equal to the image of a singleton containing that element, the singleton being a subset of $$S$$:


 * $$\forall s \in S: \mathcal{R}\left({s}\right) = \mathcal{R}\left({\left\{{s}\right\}}\right)$$.

Proof
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