[Discretespring12] Discrete Maths HW7

[Andreas Kloeckner]

Hi Kit, all,

On Sat, 31 Mar 2012 15:31:56 -0400, Kit Ying Chan <chanyinghahaha at yahoo.com.hk> wrote:
> I am confused for HW7 4.1 #24.
> The book asks us to draw a one-set arrow diagram, so does it mean
> something like figure 4-5 on page 254?

Yes.

> Or we can just draw the arrow diagram as you did in class?

No.

Here's a slightly longer answer, to try and help explain this: So far,
we've been drawing arrow diagrams for relations that were subsets 
of A x B, i.e. had a set A as their domain and a set B as their codomain.

An important special case are relations that are subsets of A x A,
i.e. have A both as their domain and codomain. These allow a
simplification in how you draw their arrow diagrams: You only draw one
copy of the set A, and then represent the relation as arrows within this
single copy of A. Figure 4-5 is an example of that.

Hope this helps,
Andreas

-- 
Andreas Kloeckner 
Room 1105A (Warren Weaver Hall), Courant Institute, NYU
http://www.cims.nyu.edu/~kloeckner/
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