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Example Questions
Example Question #1 : Set Theory
Let  denote all straight lines in the Cartesian plane. DoesÂ
,Â
, or both belong toÂ
?
 is a set that contains all straight lines that live in the Cartesian plane, this is a vast set. To determine if Â
,Â
, or both belong toÂ
, identify if the elements of each set create a straight line, and if so, then that set will be a subset ofÂ
. In other words, the set will belong toÂ
.
Identify the elements in  first.
This statement reads,  contains theÂ
 coordinate pairs that live on the lineÂ
.
SinceÂ
 is a straight line that lives in the Cartesian plane, that meansÂ
 belongs toÂ
.
Now identify the elements in .
This means that the elements of  are 2, 4, 6, and 9. These are four, individual, values that belong toÂ
. They do not create a line in the Cartesian plan and thusÂ
 does not belong toÂ
.
Therefore, answering the question,  belongs toÂ
.
Â
Â
Example Question #2 : Set Theory
Let  denote all parabolas in the Cartesian plane. DoesÂ
,Â
, or both belong toÂ
?
 is a set that contains all parabolas that live in the Cartesian plane, this is a vast set. To determine if Â
,Â
, or both belong toÂ
, identify if the elements of each set create a straight line, and if so, then that set will be a subset ofÂ
. In other words, the set will belong toÂ
.
Identify the elements in  first.
This statement reads,  contains theÂ
 coordinate pairs that live on the parabolaÂ
.
SinceÂ
 is a parabola that lives in the Cartesian plane, that meansÂ
 belongs toÂ
.
Now identify the elements in .
This means that the elements of  are those that live on the straight line
. Thus
 does not create a parabola in the Cartesian plan thereforeÂ
 does not belong toÂ
.
Therefore, answering the question,  belongs toÂ
.
Â
Example Question #1 : Set Theory
Determine if the following statement is true or false:
In accordance to primitive concepts and notations in set theory, many axioms lead to paradoxes.
True
False
False
First recall the primitive concepts and notations for set theory.
"class", "set", "belongs to"
Now, when deciding what constitutes a primitive concept, it is agreed upon in the math world that four main criteria must be met.
1. Undefined terms and axioms should be few.
2. Axioms should NOT be logically deducible from one another unless clearly expressed.
3. Axioms are able to be proved.
4. Axioms must NOT lead to paradoxes.
Thus, the statement in question is false by criteria four.
Example Question #1 : Axiomatic Set Theory
Determine if the following statement is true or false:
In accordance with primitive concepts and notations in set theory, many axioms are deducible from other axioms.
False
True
False
First recall the primitive concepts and notations for set theory.
"class", "set", "belongs to"
Now, when deciding what constitutes a primitive concept, it is agreed upon in the math world that four main criteria must be met:
1. Undefined terms and axioms should be few.
2. Axioms should NOT be logically deducible from one another unless clearly expressed.
3. Axioms are able to be proved.
4. Axioms must NOT lead to paradoxes.
Thus, the statement in question is false by criteria two.
Example Question #3 : Axiomatic Set Theory
Which of the following describes the relationship between the inhabited sets  andÂ
 ifÂ
 ?
 andÂ
 intersect.
 andÂ
 have equal cardinality.
 andÂ
 are disjoint.
 is a subset ofÂ
.
  is a subset ofÂ
.
 andÂ
 are disjoint.
If the intersection of two sets is equal to the empty set (they do not intersect, i.e. they share no elements), then the two sets are said to be disjoint.
Example Question #6 : Set Theory
Which of the following represents , whereÂ
,Â
, andÂ
 ?
To solve this problem, we first  find the union of  andÂ
; this is the set of all elements in both sets, or Â
.Â
 is simply the set of all even natural numbers. The intersection of these two sets is therefore the set of the even numbers present inÂ
, which is the set containing the numbers 2, 8, and 10.
Example Question #1 : Axiomatic Set Theory
Which of the following represents , whereÂ
,Â
, andÂ
 ?
Because  andÂ
 share no elements, their intersection isÂ
, such thatÂ
 The union ofÂ
 and any set is the set itself. Therefore,Â
.
Example Question #1 : Set Theory
For two sets,  andÂ
, which of the following correctly expressesÂ
 ?
The sum of the cardinalities of two sets is equal to the sum of the cardinalities of their intersection and union. For instance, if  andÂ
:
and,
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