Set Theory - Question 2.

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When do A and B have the same cardinal number (or #(A))?
If A is equivalent to B; A~B.
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When is #(A) = #(B)?
If and only if A ~ B.
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When is #(A) ≤ #(B)?
If and only if A ≤ B.
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What is the Schroeder-Bernstein now?
If #(A) ≤ #(B) and #(B) ≤ #(A), then #(A) = #(B).
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What is the Schroeder-Bernstein theorem?
If A ≤ B and B ≤ A, then A~B; let X¡ ¢ Y ¢ X and let X~X¡, then X~Y.
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What is a countable set?
If and only if a set is finite or denumerable.
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When is a set equivalent to N?
If and only if a set X is denumerable and has cardinality No.
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What is Cantor's Theorem?
The power set P(A) of any set A has cardinality greater than A.
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What conditions have to be satisfied for a relation ≤ to be a partial order?
If and only if for every a,b,c e A: the relation is reflexive, anti-symmetric and transitive.
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What does this mean?
If and only if for every a ,b, c e A: a ≤ a; a ≤ b and b ≤ a implies a=b; a ≤ b and b ≤ c implies a=c.
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What does totally ordered set mean?
Partially ordered set if, for every a, b e A, either a ≤ b or b ≤ a.
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Other cards in this set

Card 2

Front

When is #(A) = #(B)?

Back

If and only if A ~ B.

Card 3

Front

When is #(A) ≤ #(B)?

Back

Preview of the front of card 3

Card 4

Front

What is the Schroeder-Bernstein now?

Back

Preview of the front of card 4

Card 5

Front

What is the Schroeder-Bernstein theorem?

Back

Preview of the front of card 5
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