Relation domain

Set

context $ R $
$ c\in R $
postulate $ \forall c.\ \exists a,b.\ c=\langle a,b\rangle $
definiendum $ x\in \mathrm{dom}(R) $
postulate $ \exists y.\ \langle x,y \rangle\in R $

Discussion

Reference

Wikipedia: Domain of a function

Parents

Context

Ordered pair