1=.999999...?


Sorry, the point wasn't to be confrontational, but helpful.

Also, if I understood what you meant by "loop logic", you haven't really understood what Euclid's Elements is about. That should be something taught in philosophy classes too, but unfortunately people don't really understand it before they've personally and concretely experienced the maths themselves.

Third, it wasn't an argument. You just don't understand very well the maths, and many persons that know about it more than I do have already explained it better than I can, so why would I go through the trouble? If I explained it to you, would you go through the trouble of doing the exercises? If not, then the explaining would be useless, since you really understand maths only after you've done it yourself.

It looks like people are wilfully omitting much of the things that I've said, like 0.999.. is defined as a limit of a sequence, not as a sequence. What's the use of explaining if nobody's going to listen. (Well, actually there is use, but the ones listening aren't arguing against me).

As for argument, I already laid down my case. I haven't seen anything solid presented against it.

EDIT:
The problem, of course is if 1=0.999... why are they two different numbers? It's not so much counterintuitive, but rather illogical, as well as inconsistent.

Because the real numbers aren't a set defined by decimal numbers. First there's the real numbers, then there are the decimals. They're not ineffective only in the sense that there are real numbers that can be written down two ways. They are also ineffective in the sense that there are real numbers that can't be written down as decimals at all.
 
I haven't read most of the thread since my last post, but you guys are seriously refusing to listen.
Just stop talking about series. 0,999... is a number, and it is the same number as 1.
There is absolutely no approximation anywhere at all whatsoever
 
Sorry, the point wasn't to be confrontational, but helpful.

Also, if I understood what you meant by "loop logic", you haven't really understood what Euclid's Elements is about. That should be something taught in philosophy classes too, but unfortunately people don't really understand it before they've personally and concretely experienced the maths themselves.

Third, it wasn't an argument. You just don't understand very well the maths, and many persons that know about it more than I do have already explained it better than I can, so why would I go through the trouble? If I explained it to you, would you go through the trouble of doing the exercises? If not, then the explaining would be useless, since you really understand maths only after you've done it yourself.

It looks like people are wilfully omitting much of the things that I've said, like 0.999.. is defined as a limit of a sequence, not as a sequence. What's the use of explaining if nobody's going to listen. (Well, actually there is use, but the ones listening aren't arguing against me).

As for argument, I already laid down my case. I haven't seen anything solid presented against it.

EDIT:


Because the real numbers aren't a set defined by decimal numbers. First there's the real numbers, then there are the decimals. They're not ineffective only in the sense that there are real numbers that can be written down two ways. They are also ineffective in the sense that there are real numbers that can't be written down as decimals at all.

You aren't the only one who happens to know what a limit of a sequence is, nor what it is next to a sequence. Again, you are being confrontational. Also, what is "you don't seem to understand what Euclid is about" at all? Unless in your view that is another line which perfectly stands on its own without elaboration.

Re current definitions of the Real numbers, which obviously include also numbers not to be written as a single fraction (eg pi can be written as a sequence, or approximated geometrically as it had been since Antisthenes and Archimedes) : yes, i noted time and again that the main issue in the thread is that us non uni-degree math people are not to be expected to be aware of the way sets such as the Real numbers are currently defined (in the context covering what is being discussed here, at least). So if you just type stuff like Epsilon as you did, and then brush off the persistent notes on the argument being very counter-intuitive and indeed seemingly based on particularly set axioms, you should not really have accepted something other from the number of people here who honestly wrote down how it is not evidently consistent and asked for specific info on how it is set so as to be consistent in current axioms (and definitions) used.

So yeah, i am not at all seeing how you are in the right here. If anything you come across as needlessly arrogant, while in my view that you get asked questions should be regarded as evidence that people wanted to see what you (and i suppose current math systems re this issue) meant.

Do not take people who just do not have a uni math degree as inherently unable to follow what you say. I think we would if it was elaborated decently, and was legitimately consistent along with covering the notions discussed (Epsilon, Real numbers re fractions and other stuff, etc etc).
 
Why should anyone believe your "approximation" argument if you have to say "oh well zero is a special case so I don't have to worry about that"
Do you believe that you can divide by zero?
 
Sorry, the point wasn't to be confrontational, but helpful.

Also, if I understood what you meant by "loop logic", you haven't really understood what Euclid's Elements is about. That should be something taught in philosophy classes too, but unfortunately people don't really understand it before they've personally and concretely experienced the maths themselves.

Third, it wasn't an argument. You just don't understand very well the maths, and many persons that know about it more than I do have already explained it better than I can, so why would I go through the trouble? If I explained it to you, would you go through the trouble of doing the exercises? If not, then the explaining would be useless, since you really understand maths only after you've done it yourself.

It looks like people are wilfully omitting much of the things that I've said, like 0.999.. is defined as a limit of a sequence, not as a sequence. What's the use of explaining if nobody's going to listen. (Well, actually there is use, but the ones listening aren't arguing against me).

As for argument, I already laid down my case. I haven't seen anything solid presented against it.

EDIT:


Because the real numbers aren't a set defined by decimal numbers. First there's the real numbers, then there are the decimals. They're not ineffective only in the sense that there are real numbers that can be written down two ways. They are also ineffective in the sense that there are real numbers that can't be written down as decimals at all.

I agree this is very confrontational. It also has some fundamental errors. 0.999.. is NOT defined as the limit of a sequence. The limit is 1, so you assume your conclusion. This is a basic logical fallacy, which you should avoid.

0.999... is the sum of an infinite sequence, also called a series. That is 0.9+0.09+0.009+... This series is strictly less than 1, with an undefined difference. It is an element of the open segment (0,1), which 1 is not.

If you wish to show your greater knowledge, demonstrate that 0.9999... is not an element of (0,1) without resorting to limits. Since the limit of the series is not identical to the sum of the sequence, that is your often repeated fallacy.

J
 
Do the same thing with 0.999...

x = 0.999...

10x = 9.999...

10x - x = 9

9x = 9

x = 1


I don't really understand the "they can't have the same value because they look different on paper" objection. 2/2 and 1 have the same value despite looking different.

Looks convincing to me! :goodjob:

Here's a vid to play in the background while pondering this thorny subject.
It helps improve concentration. :)


Link to video.
 
Only, apparently, because it is defined that way. It's interesting to compare the rigid invariance from a single set of definitions in this case with the existence of multiple systems in physics - SI & cgs for example.
 
You aren't the only one who happens to know what a limit of a sequence is, nor what it is next to a sequence.

Well, if you think the talk about epsilons was cryptic, your notion of the limit is not very well founded. You may not know that, but I and many others in this thread do. That's why I've brought degrees into the discussion: it should give you a hint that instead of arguing against you might do yourself a service by listening.

Another thing that you may not notice is that half of what you write (and this goes to Onejayhawk and in a lesser dergree to Brennan too) is impossible to decipher. That's because you use words from your intuitive understanding, but haven't stopped to think what they mean, or whether that meaning could be consistent. Again, this isn't something you could expect from a layman. Just like you'd expect that I have lesser understanding of Platon's dialogues than you. This isn't any small phenomenon, but extremely overwhelming, for almost every sentence that you've written I could write a page as a response or questions. This is like learning a language or a game: you have to achieve a certain amount of knowledge before you can do anything of substance.

As an example, in the above quote, I can't even imagine what limit being "next to a sequence" could mean.

If I sound hostile, well, sorry, it's unintentional, but it's partly due to the frustration over this gap in communication. To make that gap smaller, you would have to study some maths. Just like I can't speak Greek to you without putting an effort into learning it.

Again, you are being confrontational. Also, what is "you don't seem to understand what Euclid is about" at all? Unless in your view that is another line which perfectly stands on its own without elaboration.

I thought it would be a line that would make you think: "Perhaps I should check into this one more time". The point was that this:
from the stuff posted in the thread it is pretty obvious that this is an issue of closed loop logic, ie it can be perfectly valid in the current math field, but it is not explainable without providing elaborate info on the axioms which close up this logic and limit the definitions used.

holds as much on Euclid's Elements as it does on this topic. Euclid's theorems are valid in his text, but aren't explainable without providing (less) elaborate info on the axioms which close up this logic and limit the definitions used. That's the whole point of the maths, that's why Euclid is considered to be as great as he is.

and then brush off the persistent notes on the argument being very counter-intuitive and indeed seemingly based on particularly set axioms, you should not really have accepted something other from the number of people here who honestly wrote down how it is not evidently consistent and asked for specific info on how it is set so as to be consistent in current axioms (and definitions) used.

What is not evidenetly consistent? What is set to be so as to be consistent in current axioms? I honestly don't understand a bit of this.

Also, I haven't seen anyone pointing out any inconsistencies in the proof. I have seen people stubbornly claiming that 0.999... is a process etc., but I haven't seen anyone point out any inconsistency.

So yeah, i am not at all seeing how you are in the right here. If anything you come across as needlessly arrogant, while in my view that you get asked questions should be regarded as evidence that people wanted to see what you (and i suppose current math systems re this issue) meant.

That's not at all how it looks to me. I don't think anyone posted any questions on it. It looks like no one even read it. On the contrary, I find it arrogant that some posters here claim superior knowledge over professionals without giving a single clue on where that knowledge comes from.

Do not take people who just do not have a uni math degree as inherently unable to follow what you say. I think we would if it was elaborated decently, and was legitimately consistent along with covering the notions discussed (Epsilon, Real numbers re fractions and other stuff, etc etc).

Yes, and for that there are books and courses. This thing can't be taught thoroughly in a forum post. That's just a thing you have to accept. I can't expect you to give me full disclosure on ancient Greek philosophy either. If I want to know, I read a book.

There's also been numerous easy access proofs here, that may not tell the thing exactly, but are enough to satisfy most laymen.

For example the thing of multiplying by ten and subtracting 0.999... is a very fine method.

(Similar method also btw, is useful to find out what a decimal with recurring digits is as a fraction. For example,
0.123123... *1000 = 123.123123...
so 999* 0.123123... = 123
and thus 0.123123... = 123/999.

This is especially funny, since there's been claims in this thread that 0.999... is a transcendent number, and this is an easy way to see that a number is rational).

0.999.. is NOT defined as the limit of a sequence.

Then how it is defined?

That's the minimum amount of information you should provide if you want to claim anything about the number.

0.999... is the sum of an infinite sequence, also called a series. That is 0.9+0.09+0.009+... This series is strictly less than 1, with an undefined difference. It is an element of the open segment (0,1), which 1 is not.

If you wish to show your greater knowledge, demonstrate that 0.9999... is not an element of (0,1) without resorting to limits. Since the limit of the series is not identical to the sum of the sequence, that is your often repeated fallacy.

1. An infinite sequence isn't called a series.
2. What is "an undefined difference"?
2.1. How can you do even the simplest of maths, if there's no guarantee that subtraction works.
For example, to solve x from x+y=1 you should take into account the possibility that y=0.999... Do you write in the margin those exceptions, do you check them at the end of the calculations. Yes, I know that zero does the same thing when you divide by it, but those things are checked separately).
3. What exactly is strictly less than 1?
4. I have provided already an example of a sequence with elements strictly less than 1, but whose limit is 1.
5. Why shouldn't I resort to limits?
6. Series doesn't have limit.
7. Sum of a series is defined to be the limit of the partial sums. If you have other knowledge, please tell us the definition. You're also welcome to give reference to some real mathematical work that uses your definition.

But most of all, tell us what do you think 0.999... means. How do you think it's defined?
 
If you wish to show your greater knowledge, demonstrate that 0.9999... is not an element of (0,1) without resorting to limits. Since the limit of the series is not identical to the sum of the sequence, that is your often repeated fallacy.

Easy:

The definition of an open interval is:
An interval is said to be left-open if and only if it has no minimum (an element that is smaller than all other elements); right-open if it has no maximum; and open if it has both properties.

So let us assume that 0.99... is an element of (0,1).
There is no number x that fulfills: 0.99... < x < 1 (I could formalize this step further if you do not believe that). Therefore 0.99... would be the maximum of (0,1), which is not possible by definition. Thus we have a contradiction, the premise has to be wrong, and 0.99... cannot be an element of (0,1). q.e.d.

You are still making the fundamental error, that a series has a limit. It has not. If a series is convergent, it is exactly one real number. It is the limit of its sequence of partial sums, but that is a different statement.
 
@Uppi and Atticus:

What the non-math degree posters claim (at least myself, but i think the other three are likely not saying that different things) is that we do not see just why it apparently is axiom-set that it is fine to use multiplication and like actions on a "number" like 0.99999.... which exactly has no set ending decimal part. Isn't this a bit like saying that an immobile object and a runner are both 'running' and thus we can view them as functions of 'running'? 0.9999... is not a specific number, and if you define it as the limit of sequences such as 0.9+0.09+0.009+... then isn't the set limit this sequence converged to the number 1? (which is outside of the sequence anyway?).

That is what we are asking (or at least mainly) : why is a limit taken to mean both the actual limit (1 in the above case) and an ongoing and non-ending reach for that limit? (0.999..... in that case). If you just set it axiomatically as that then we can accept it as an axiom, but axioms by definition are not provable within the context they define.

(Now, not from posts written, but from stuff inferred, i suppose there is some elaboration of this reasoning in current math, but we were not told what to look for at any rate)

(re Euklid, well, do not worry, i at least know what axioms are, let alone that officially they begin almost 4 aeons prior to Euklid, with Thales ;) ).
 
why is a limit taken to mean both the actual limit (1 in the above case) and an ongoing and non-ending reach for that limit? (0.999..... in that case).

It doesn't mean the ongoing and non-ending reach to that limit.

Say you have a sequence 1, 1/2, 1/3,.... It's limit is 0. That 0 isn't the same thing as the sequence. It's just a number.

Similarly, 0.999... is a limit of a certain sequence. As it happens, that limit is 1. The limit isn't the sequence anymore, just like 6 isn't addition or subtraction, although you can get 6 as 4+2 or 7-1.


Why you can treat it as a normal number:
As said before, decimal numbers aren't needed for anything. It's possible to do maths without them. They however are useful in physics, engineering etc., and 1.75 tells you quicker how big a number is than 7/4 for example.

So, they are nice and useful thing. Then they must be defined. For big part that's just a matter of taste. They could be defined for example so that no ellipses are allowed. You would be allowed to write as decimals only things like 1.75 or 23.343, but not 0.333...

For some reason that's not enough for people, so there's this more permissive definition that allows ellipses. That there is a number like 0.9999... is then just a matter of convenience. To write a number like that is something a nasty school boy would do. No sane person would write for example 2 - 1 = 0.9999.... Not because it would be wrong, but because it's obfuscated, just like it would be stupid to write 2-1=37/37 (unless you have some specific reason to do so).

So, the number 0.999... isn't a thing people use. It's just a curiosity that comes from "misuse" of the notation. No one in his right mind would use that notation anyhow, so it's easier to allow it than to make specific rules prohibiting it.

(There are some cases when this becomes relevant though, like Cantor's diagonal proof, which would have perhaps been better to leave unmentioned, since this thread will be nothing compared to the crap storm that topic brings up. :D)
 
Maybe I should just grab &#8216;Riddles in Mathematics&#8217;, scan it, paste the image here and be done with the Cantorian crapstorm?
 
I have a totally lay question then,

What's the difference between [0,1] and [0,1)? To my lay understanding, it means that the interval doesn't include 1. Am I right? And is there such this as a 'the biggest number' for each set?
 
Yep, that's the difference. One set ends at 1, the other includes every number prior to 1 but not 1 itself.

Edit: that was from memory. Including more formal quote form [wiki=Set_notation]wiki[/wiki]:
The convention for denoting intervals uses brackets and parentheses, depending as the corresponding endpoint is included in or excluded from the set, respectively. Thus the set of reals with absolute value less than one is denoted by (&#8722;1, 1) &#8212; note that this is very different from the ordered pair with first entry &#8722;1 and second entry 1. As other examples, the set of reals x that satisfy 2 < x &#8804; 5 is denoted by (2, 5], and the set of nonnegative reals is denoted by [0, &#8734;).​
So there's no biggest number for [0,1) then.
 
Do you believe that you can divide by zero?
No. But, to my knowledge, nobody has a competing mathematical system that does everything the present one does except allow one to divide by zero. Atticus and Leifmk (and in fact the entirety of mainstream maths) have a system that works for all digits, with no apparent drawbacks (other than making you wrong of course).

Why would anyone use your system, which works for 9/10 digits, when they can use Atticus's system, which works for 10/10 digits? Hand wave it away if you like, but I'm not buying an approximation of how maths works; I want the real thing.
 
No. But, to my knowledge, nobody has a competing mathematical system that does everything the present one does except allow one to divide by zero. Atticus and Leifmk (and in fact the entirety of mainstream maths) have a system that works for all digits, with no apparent drawbacks (other than making you wrong of course).

Why would anyone use your system, which works for 9/10 digits, when they can use Atticus's system, which works for 10/10 digits? Hand wave it away if you like, but I'm not buying an approximation of how maths works; I want the real thing.

What is being discussed, though, is not using numbers for counting. That is always done with the notion of the integer. The issue discussed is how Real numbers are currently defined, at least in cases such as the now infamous here 0.9999..... ;)

Afaik in most systems no 'number' actually has a unique meaning. By and large if the focus is in small parts of systems (eg natural series), you can get away with just examining a series diverging to infinity by viewing it as iteration of 1 (1, 1+1, 1+1+1, ...) without actually definining "1" in regards to a unified number (sorry Atticus, this is on Plato and friends, so you'll have to deal with philo jargon yourself :p ).

In a sequence that has a limit at (for example) "1", that "1" (as Atticus also said) is not tied to the sequence, and is just a number, thus it can be an infinite amount of stuff and is not a unique object in regards to the sequence. But (IIRC) in some differently set systems (hyperbolic geometry?) you can actually see the axioms lead to some 'numbers' or other properties being less populous in regards to how they can appear (stressing the IIRC here, cause i am not fluent in it: i think that in hyperbolic geometry you can even have a maximum sized closed shape? such as a triangle and so on?).

Anyway, math= meth. I always postpone actually looking into this more deeply. Maybe also cause my childhood dream (up to late highschool) was exactly to be a notable mathematician, but stuff prevented me from that :)
 
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