By A CooperWe know that is the smallest infinite set; this makes a pretty good place to get started. But our ideas about size have to do... |cardinality

By A CooperGrab some collection of objects and count it. How does that work? Let's say we want to count the (living) former Presidents of the United... |functions

By A CooperRecall that we defined inverses for any relation: Definition. If is a relation from to , then is a relation from to , defined by... |functions

By A CooperConsider the set of all functions . Each subset has such a function, namely its characteristic function, ; moreover, given we can define the set... |functions

By A CooperPushforwards and Pullbacks A function gives us a way of taking elements in and pushing them over to . We call the image of under... |functions