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1 + 1 (mander.xyz)

submitted 3 months ago by fossilesque@mander.xyz to c/science_memes@mander.xyz

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[-] FiskFisk33@startrek.website 27 points 3 months ago* (last edited 3 months ago)

ok, I define 1 as {∅} and 2 as {∅, {∅}}

proving the addition holds is slightly more complicated

[-] Wilzax@lemmy.world 11 points 3 months ago

Now define "+"

[-] FiskFisk33@startrek.website 30 points 3 months ago

I love the comment that it's "occasionally useful"

[-] Wilzax@lemmy.world 15 points 3 months ago

Hmm yes.. set theory... I don't understand anything happening here

[-] FiskFisk33@startrek.website 12 points 3 months ago* (last edited 3 months ago)

There is actually a really good explanation for us math-curious non-mathematicians here:
https://blog.plover.com/math/PM.html

[-] MaliciousKebab@sh.itjust.works 3 points 3 months ago

That's some good read, thank you so much.

[-] MBM@lemmings.world 7 points 3 months ago

+ is a map from N×N to N where a + 0 = a and a + S(b) = S(a + b) (S is the successor function that gives the next number).
Then 1 + 1 = 1 + S(0) = S(1 + 0) = S(1) = 2.

[-] funkless_eck@sh.itjust.works 4 points 3 months ago

seems a little sus to use + to define +

[-] apolo399@lemmy.world 8 points 3 months ago

No, it's correct. You define the operation by it's properties. It's not saying that "a plus 0 = a" but "the result of applying the binary operation '+' to any number with 0 should give the original number."

is just a symbol. You could instead write it as +(a,0)=a and +(a,S(b))=S(+(a,b)).

You have to have previously defined 1=S(0), 2=S(1), 3=S(2), and so on.

[-] porl@lemmy.world 4 points 3 months ago

I really recommend the YouTube channel "Another Roof". His first few videos were building up exactly this idea, as well as building up all the real numbers (possibly complex too if I'm remembering correctly). Sounds like a dry topic but he uses humour really well throughout. https://youtube.com/@anotherroof