subsets of Universe

[Kaycee]

Is S is a subset of universe U, find each of the following:
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S U S with a line on top of the second S

_
U

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S n S

 

[stapel]

What does "line on the top of" mean?

What have you tried? How far have you gotten?

Eliz.

 

[pka]

Instead of overline used for complement let us use A<SUP>c</SUP>.
A<SUP>c</SUP> is the set of all elements in U that are not in A.
Thus A<SUP>c</SUP>∪A must be U, because any x∈U is either in A or not in A.
Moreover, A<SUP>c</SUP>∩A=∅ because no element is both in A and not in A.