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
| 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 $ |
Wikipedia: Domain of a function