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[-] BachenBenno@feddit.de 5 points 6 months ago

Mathematics is built on axioms that have nothing to do with numbers yet. That means that things like decimal numbers need definitions. And in the definition of decimals is literally included that if you have only nines at a certain point behind the dot, it is the same as increasing the decimal in front of the first nine by one.

[-] Sop@lemmy.blahaj.zone 24 points 6 months ago

That’s not an axiom or definition, it’s a consequence of the axioms that define arithmetic and can therefore be proven.

[-] JohnDClay@sh.itjust.works -4 points 6 months ago

There are versions of math where that isn't true, with infinitesimals that are not equal to zero. So I think it is an axium rather than a provable conclusion.

[-] JackRiddle@sh.itjust.works 7 points 6 months ago

Those versions have different axioms from which different things can be proven, but we don't define 9.9 repeating as 1

[-] Feathercrown@lemmy.world 2 points 5 months ago

That's not what "axiom" means

[-] aoidenpa@lemmy.world 12 points 6 months ago* (last edited 5 months ago)

That's not how it's defined. 0.99.. is the limit of a sequence and it is precisely 1. 0.99.. is the summation of infinite number of numbers and we don't know how to do that if it isn't defined. (0.9 + 0.09 + 0.009...) It is defined by the limit of the partial sums, 0.9, 0.99, 0.999... The limit of this sequence is 1. Sorry if this came out rude. It is more of a general comment.

[-] BachenBenno@feddit.de -2 points 5 months ago

I study mathematics at university and I remember it being in the definition, but since it follows from the sum's limit anyways it probably was just there for claritie's sake. So I guess we're both right...

this post was submitted on 27 Jun 2024
817 points (95.2% liked)

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