Talk:Discrete Mathematics/Functions and relations

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Lots of material there, maybe enough for several "modules". Would it make sense to divide it up ? -- Karl Wick

I'd be against the idea, in my opinion. If someone's trying to study the material, it'd be a great deal more difficult jumping back and forth through linking to other modules. Anyway, this module's almost done, just going to cover Hasse diagrams and some questions/answers and I'm done with this bit, I think. Dysprosia 10:20, 5 Sep 2003 (UTC)

[edit] Confusion about Cartesian product definition of Function

I was reading the Other function notation section of this module and was a bit confused by the wording of the last sentence:

So using set notation, a function can be expressed as the Cartesian product of its domain and range.

Shouldn't that read a function can be expressed **as a subset of** the Cartesian product of its domain and range.? Otherwise, the function would be defined as F={(1,1),(1,4),(1,9),(2,1),(2,4),(2,9),(3,1),(3,4),(3,9)}.

Or perhaps my understanding of a Cartesian product is incorrect. Just wanted some clarification. Thank you.

This confuses me too. Tim J Tylor (talk) 11:06, 23 April 2008 (UTC)

I think there is a short coming in the discussions of functions nothing has been mentioned one to one function or generally the types of functions

[edit] OR or XOR in trichotomy

I just added an example in the Trichotomy section but I'd like to know if the or we have is a strict OR (XOR) or not. If it is then my example is incorrect (since sometimes both aRb and bRa hold).

Thanks for your help :)