OP, I need the definition for × and <,> too
× is the cartesian product I think, no clue what the other thing is tho
× is the cartesian product and = {x, {x,y}} is the ordered pair of x and y. (i.e., if x is in X and y is in Y, then is the corresponding element of the cartesian product X × Y). hope this helps
Oh wow, I should know that… Thanks
What does type() mean here?
it’s the “order type” of a well ordering on a set. so, given a set X with a total ordering R, type(X,R) is the unique ordinal isomorphic to (X,R)
what’s with the square at the end? isn’t that usually for proofs?
yeah but sometimes when the textbook authors are feeling particularly mischievous they’ll just put them in random places. and sometimes they’ll even skip the proofs but keep the square.
Give it up for op actually out here answering questions like a real live teacher.
