If you have a question, the answer is probably of interest to everybody in the course. I will therefore post questions and answers on this page.
Q: Can you have a map f : A -> B such that every 'a' in A has several f(a) in set B?
A: No. Each 'a' in A is mapped to a single f(a) in B.
Q: If we see Y\X, is it safe to assume that X is a subset of Y?
A: Yes.
Q: What does "the set of all maps from A to B" mean?
A: The set B^A is the set whose elements are the maps f : A->B. For example if A = {a} and B = {x,y} then there are two elements in B^A: the map {f : a -> x} and the map {g : a -> y}.
Q: What does "pairwise distinct" mean (HW2, problem A.2)?
A: It means that any two are different.
Q: What does Q* (in HW2, problem B.1) mean?
A: all the elements of Q different from 0.
Q: In problem HW5 A.2, would f^2(x) mean f iterated twice as problem C.2 suggests?
A: No, in this case it does mean f squared.
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A: