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addition rule (lemmy.world)
submitted 11 months ago by affiliate@lemmy.world to c/196@lemmy.blahaj.zone
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[-] affiliate@lemmy.world 28 points 11 months ago

× 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

[-] rasensprenger@feddit.de 12 points 11 months ago
[-] affiliate@lemmy.world 25 points 11 months ago

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)

[-] bort@feddit.de 11 points 11 months ago

what's with the square at the end? isn't that usually for proofs?

[-] affiliate@lemmy.world 15 points 11 months ago

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.

[-] Lemjukes@lemm.ee 8 points 11 months ago

Give it up for op actually out here answering questions like a real live teacher.

[-] Sasha@lemmy.blahaj.zone 2 points 11 months ago

Oh wow, I should know that... Thanks

this post was submitted on 01 Feb 2024
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