I am reading Halmos’s Naive Set Theory. He writes:
If $R = X \times F$, then $\mbox{dom } R = X$ and $\mbox{ran } R = Y$.
I am confused by this. If $X \times Y = R$, wouldn’t $\mbox{dom } R = X$ and $\mbox{ran } R = Y$? Thanks in advance.
2026-03-25 23:36:44.1774481804
Halmos on domain and range of relations
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I've just found out there is a typo in the kindle edition of Naive Set Theory by Halmos. In this version https://books.google.com.au/books?id=x6cZBQ9qtgoC&pg=PA26&source=gbs_toc_r&cad=2#v=onepage&q&f=false he has used Y not F.