Search All of the Math Forum:
Views expressed in these public forums are not endorsed by
Drexel University or The Math Forum.



Re: Transitive closure that is reflexive?
Posted:
Sep 24, 2001 1:14 AM


In article <9ok0rg$sog$1@news.state.mn.us>, <zgene@hotmail.com> wrote:
>I am kinda new to discrete mathematics. I am reading a book by Harry >Lewis, in which I find some confusing sentences. Here is one:
>a binary relation that is not reflexive but has a transitive closure that >is reflexive.
That is not a sentence. It has no verb. Are you saying there is some particular binary relation that has these properties? It certainly is not true of all binary relations.
>I understand 'reflexive', but just don't get 'transitive closure', and a >'transitive closure that is reflexive'. So confusing.
>Can you guys help explain this to me with an example? Thanks a lot.
Consider the notequal relation R on any set X having at least two members. R is not reflexive, but its transitive closure R' is reflexive, because for each x in X there exists y in X such that xRy and yRx (meaning x != y and y != x). Hence (x,x) is in R', the transitive closure of R.
 Dave Seaman dseaman@purdue.edu Amnesty International calls for new trial for Mumia AbuJamal



