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Topic: More on Venn...
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Alfred Barron (908) 704-4102

Posts: 30
Registered: 12/6/04
More on Venn...
Posted: Dec 7, 1995 10:58 AM
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Venn diagrams are useful devices for illustrating abstract concepts
of algebraic operations defined on 'ordinary' sets. The basic oper-
ations are union (if A and B are sets, this is the set of all elements
in either A or B or both), intersection (the set of all elements in
both A and B), complementation (the set of elements not contained in
a set A, call A'), and inclusion (every element of A is an element of
B). Note that this last operation can be interpreted as 'A implies B'
or as 'B is implied by A'.

With respect to inclusion, clearly the city of Alberquerque is in the
state of New Mexico. If two venn diagrams are drawn intersecting, then
yes, this is logically equivalent to the inclusion statement, provided
one of the nonintersecting circles has no elements, i.e., is empty.

The existence of the empty set follows logically as the set with no
elements. Its size is zero. Equivalently, the probability of an impos-
sible event is zero. Logically this is as fundamental as the concept
of the number zero.

Speaking of sets and all that, what ever happened to Dolciani, et al.?
Both my wife and I first learned of set theory from her series of
textbooks (no, I didn't know my wife in HS).

Al Barron

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