Mathematics for Computer Science

“mcs” — 2017/3/3 — 11:21 — page 118 — #126
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Chapter 4
Mathematical Data Types
(b) The set of pages containing the word “set” that have been recommended by
“Meyer”
(c) The set of endorsers who have recommended pages containing the word “algebra”
(d) The relation that relates endorser e and word w iff e has recommended a page
containing w
(e) The set of pages that have at least one incoming or outgoing link
(f) The relation that relates word w and page p iff w appears on a page that links
to p
(g) The relation that relates word w and endorser e iff w appears on a page that
links to a page that e recommends
(h) The relation that relates pages p 1 and p 2 iff p 2 can be reached from p 1 by
following a sequence of exactly 3 links
Exam Problems
Problem 4.29.
Let A be the set containing the five sets: fag; fb; cg; fb; dg; fa; eg; fe; f g, and let
B be the set containing the three sets: fa; bg; fb; c; dg; fe; f g. Let R be the “is
subset of” binary relation from A to B defined by the rule:
X R Y IFF X Y:
(a) Fill in the arrows so the following figure describes the graph of the relation,
R: