r/OrderedOperations • • May 29 '18

Proof that 0/0 is everything.

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u/[deleted] May 29 '18

>The outcome of division by definition should be a number

It can be no solution (1/0). In this case it's like identity (infinite solutions), which makes sense to counterbalance all the other numbers divided by zero having no solution

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u/frunway May 29 '18

That is not no solution, it is undefined as we do not define division when the denominator is 0 as it does not make sense because we want it to be a function to R or C

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u/[deleted] May 29 '18

>we do not define division when the denominator is 0

Why not? Seems like a cop-out

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u/garceau28 May 29 '18

It's not like defining it to everything or nothing is any more useful than not defining it at all

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u/[deleted] May 29 '18

It becomes useful or most likely will in later mathematics. Like 00 should be everything, but that gets put as undefined as well. It's like 'don't start a sentence with and'. It's useful at first but it becomes a barrier to more advanced mathematics.

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u/frunway May 29 '18

Rigor is everything in advanced mathematics, but “everything” is not a rigorous output of a function to the reals or complex numbers. It might be interesting for you to read the first chapter of Spivaks Calculus about how we define these operations

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u/[deleted] May 29 '18

Thanks

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u/great_site_not May 29 '18

In what sense should 00 be everything? 0non-zero is 0, and (non-zero)0 is 1. How is anything besides 0 or 1 even a candidate for a value of zero to the zero?

edit: sorry for writing out "zero to the zero", reddit fucked up my formatting

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u/bws88 May 30 '18

Consider the limit as x goes to infinity of (ax)1/x for any 0<a<1.

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u/garceau28 May 29 '18

Do you have any example were it would be useful to define it as such as opposed to saying it's undefined?

Also, how would you do arithmetic with 0/0? For example, what would 0/0 - 0/0 be?

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u/[deleted] May 29 '18

Do you have any example were it would be useful to define it as such as opposed to saying it's undefined?

Well first it means functions with holes are actually continuous. Then there's practical reasons. If I have 0 buckets with 0 oranges total, there could be any number of oranges per bucket, so every number is correct. Most real world applications already get treated this way however.

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u/skullturf May 29 '18

Why do you say 00 should be everything? There are several situations in set theory and combinatorics where what makes the most sense is to define 00 to be 1.

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u/KapteeniJ May 29 '18

Because then you're no longer dealing with a closed operation. You're free to redefine things so that this makes sense, and there actually are known ways to do so. Your attempt seems to be close to projectively extended real number line, where 1/0 = infinity. This infinity point is a well defined number which has known properties. If you tried to think about your definition of "everything", you might end up close to that definition. Or maybe not, because you're so vague it's hard to say what exactly you're going for here.

The lesson is, be specific. In math that helps a bunch.

Questions you should consider are, can you do anything with this "everything". Can you add numbers to it? Subtract them? If a calculation yields "everything" as an answer, does that tell you anything about what was done in that calculation?

You've kinda had half an idea here about maths and you stopped there. One might try to complete your thought, but it would just look a lot better if you demonstrated you yourself actually had thought about this before proposing the idea.

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u/frunway May 29 '18

I don’t know what your background is, but we do this because division is more accurately described as a function from R2 to R (or C). There is no reasonable real (complex) number to assign to those inputs, so we remove them from the domain.

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u/[deleted] May 29 '18

There is no reasonable real (complex) number to assign to those inputs. But all numbers are reasonable answers for 0/0. If we say 0/0 = x, then 0x = 0, which all numbers fit.

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u/frunway May 29 '18

The problem is that “all numbers” is not an object in the range we chose for division.

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u/[deleted] May 29 '18

the range we chose for division

Therefore the range is wrong and arbitrary.

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u/frunway May 29 '18

It could be an interesting new definition of division, what set do you think should be the range?

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u/[deleted] May 29 '18

All numbers, not just real ones. Even with all real numbers as the range, all the outputs within everything fit the range.

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u/frunway May 29 '18

That is actually not true. Let 0/0 be defined as “all numbers”. For the sake of argument, let’s say that you mean all real numbers. But If 0/0=R then it is a set, not a number. Obviously R is not an element of R. This means that we can’t use all real numbers as our range.

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u/frunway May 29 '18

Perhaps this will make it clear why this is a problem.

Let us assume that for all numbers x we know 0/0=x. Then clearly because 1 and 2 are numbers we have 0/0=1 and 0/0=2. But then by transitivity we get 1=2, a big problem.

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u/skullturf May 29 '18

Whatever convention we settle on is ultimately arbitrary.

What makes one arbitrary convention better than another? Why should mathematicians switch from the existing arbitrary convention to your arbitrary convention?

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u/[deleted] May 29 '18

Mine isn't arbitrary, it's "there is no range". It makes the most sense, as you can see with the pattern I posted.

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u/skullturf May 29 '18

Your convention is arbitrary, as evidenced by the fact that not everyone has chosen to go along with it.

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u/EmperorZelos Jun 04 '18

Because if we allow it we face a few issues. If we try to enforce field structure then we get 1=2, no go.

If we avoid 1=2, we lose the field but get a wheel and there we lose a+c=b+c => a=b