The domain, range and field of a relation exist

It is important to know that the domain and range of a relation exist.

Proof that domain exists

We are given a relation [ilmath]R[/ilmath] and wish to show the set [math]\{x|\exists y:(x,y)\in R\}[/math] exists, to do this we require the axioms of schema and union.

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TODO: do this

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Set Theory

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