Chapter 5.2: Comparing the Size of Sets Flashcards
1
Q
How can we show two sets have the same size?
A
The are two injections: s -> t and t -> s
2
Q
How do we know if a set is infinite?
A
There is an injection s -> s that is not a surjection
3
Q
When is a set countable?
A
If there is an injection s -> N
