Image of Union under Relation

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

Theorem
The image of the union is equal to the union of the images.

Let $$S_1$$ and $$S_2$$ be subsets of $$S$$.

Then $$\mathcal R \left({S_1 \cup S_2}\right) = \mathcal R \left({S_1}\right) \cup \mathcal R \left({S_2}\right)$$.

Generalized Result
Let $$S_i \subseteq S: i \in \N_n$$.

Then $$\mathcal R \left({\bigcup_{i = 1}^n S_i}\right) = \bigcup_{i = 1}^n \mathcal R \left({S_i}\right)$$.

Proof
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Generalized Proof
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