Set Theory

Question 1

What does ∈ mean?

Answer 1

x is a member of y

Question 2

What does ∉ mean?

Answer 2

x is not a member of y

Question 3

What does ⊆ mean?

Answer 3

x is a subset of y ( x can also be a subset of itself )

Question 4

What does ⊂ mean?

Answer 4

x is a proper subset of y ( x cannot be a subset of itself )

Question 5

What does { x | x is odd and 10 < x < 20 }

Answer 5

Take a member ‘x’ such that x is odd and it is between 10 and 20

Question 6

Does order matter in sets?

Answer 6

No

Question 7

Does the number of times a number is repeated in a set matter?

Answer 7

No

Question 8

What does AxB mean?

Answer 8

The cartesian product of A and B (The set of ordered pairs)

For example:

{a, b} x {d, e} -> { { a, d }, { a, e }, { b, d }, { b, e } }

Question 9

What is a power set?

Answer 9

The set of all subsets of a given set (Including the empty set and the set itself)

Question 10

What is a proper subset?

Answer 10

A subset of set N that cannot be N itself

Question 11

What is the cardinality of a set?

Answer 11

The size of the set

Question 12

How to work out the cardinality of a power set?

Answer 12

2^(Cardinality of base set)

Question 13

What is the cardinality of { { a, b }, { a, c }, { c, d } }

Answer 13

3