Science Memes

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I just cited myself. (mander.xyz)

submitted 6 months ago by [email protected] to c/[email protected]

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[–] UnderpantsWeevil 19 points 5 months ago (3 children)

There's a Real Analysis proof for it and everything.

Basically boils down to

If 0.(9) != 1 then there must be some value between 0.(9) and 1.
We know such a number cannot exist, because for any given discrete value (say 0.999...9) there is a number (0.999...99) that is between that discrete value and 0.(9)
Therefore, no value exists between 0.(9) and 1.
So 0.(9) = 1

[–] [email protected] 8 points 5 months ago (1 children)

Even simpler: 1 = 3 * 1/3

1/3 =0.333333....

1/3 + 1/3 + 1/3 = 0.99999999... = 1

[–] UnderpantsWeevil 2 points 5 months ago (1 children)

Even simpler

0.99999999… = 1

But you're just restating the premise here. You haven't proven the two are equal.

1/3 =0.333333…

This step

1/3 + 1/3 + 1/3 = 0.99999999…

And this step

Aren't well-defined. You're relying on division short-hand rather than a real proof.

[–] [email protected] 1 points 5 months ago (1 children)

ELI5

[–] UnderpantsWeevil 2 points 5 months ago

Mostly boils down to the pedantry of explaining why 1/3 = 0.(3) and what 0.(3) actually means.

[–] [email protected] 3 points 5 months ago (1 children)

the explanation (not proof tbf) that actually satisfies my brain is that we're dealing with infinite repeating digits here, which is what allows something that on the surface doesn't make sense to actually be true.

[–] UnderpantsWeevil 2 points 5 months ago

Infinite repeating digits produce what is understood as a Limit. And Limits are fundamental to proof-based mathematics, when your goal is to demonstrate an infinite sum or series has a finite total.

[–] beejboytyson 2 points 5 months ago

That actually makes sense, thank you.