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Proof that .999~=1

Name: Anonymous 2007-06-26 6:16 ID:3WO6C39P

Name: Anonymous 2007-06-26 6:39 ID:JyJwTiSm

>>1
nice try rickrollin' dawg, maybe next time learn how to make proper links.

Name: RedCream 2007-06-26 15:33 ID:wvzEN2Al

x = 0.999...
10x = 9.999...
10x-x = 9.999... - 0.999...
9x = 9.000...
x = 1 : Q.E.D.

Name: Anonymous 2007-06-26 15:39 ID:Heaven

this shit is nonsense

Name: RedCream 2007-06-26 15:42 ID:wvzEN2Al

Well, #4, point out the flaw in my reasoning.  Or, STFU.  I'm OK with either result.

Name: Anonymous 2007-06-26 17:00 ID:pkuEItwZ

i was going to give the proof from my real analysis book, but its not worth it.

Name: Anonymous 2007-06-26 17:31 ID:Heaven

please no one respond to this, just trollin'.

This has been done to death. Pleeeeeeease not another one.

Name: RedCream 2007-06-27 0:23 ID:78eLBMQd

#6, your response was not one of the two options I said were valid.  I'm blocking your IP address now and I hope that teaches you a lesson or two.

Name: Anonymous 2007-06-27 0:40 ID:Heaven

>>5
The flaw is, go fuck yourself

Name: Anonymous 2007-06-27 3:00 ID:Lw1Rl6tm

Just chiming in, even though it's a rickroll:

.99999=1 in our written mathematical system, and all practical (not really) applications of it.

Logically .99999=.99999 and 1=1. Too bad you can't write that in number form. We use .99999=1 because it's impossible to work with infinity. It's a flaw in translation and nothing else.

Name: Anonymous 2007-06-27 3:08 ID:Lw1Rl6tm

>>10 here.

I don't think I made it clear, I meant .99999=1 is correct in our mathematical system. It's only incorrect when looked at outside of numbers IE: how can something that only approaches 1 equal 1?

When written down. it's correct.

Name: RedCream 2007-06-27 4:07 ID:YYvLkeo7

#9's panties are obviously in a bunch.  I recommend a good gynecologist.

#11, are you saying that the flaw in my method is that shifting the decimal point on an infinite series can't be equated with another infinite series?  In other words:

 If a = 0.999...,
 and 10b = 9.999...,
 then 10b-a =/= 9 ?

Would it be correct to say instead:

  10b-a = 9+lim(->0) ?

Sorry if I'm committing a massacre of mathematical notation here.

Name: Anonymous 2007-06-27 4:21 ID:UpCvDXAy

dear redcream, this is >>6
i was going to give the proof of repeating decimals ending in 0s being = to the corresponding one of 9s, but you can pretend i was 4 if you want.  i decided the LOL THEYRE NOT THE SAME KEKE trolls are boring, and trolling.

Name: Anonymous 2007-06-27 7:05 ID:P6+Eeh8E

This is stupid...

 10 is correct.

 ...why don't we use names?

Name: Anonymous 2007-06-27 9:03 ID:+ddmTCRZ

>>10

That's horrible maths.

Basically, one way to construct the real numbers from the set of rationals, which are easily constructed from the naturals, which can be constructed from the empty set, Is to define each real number as the limit of a cauchy sequence.

From this definition and the basic definition of a limit it's obvious that 0.9999~ = 1 as 0.9999~ is defined as the limit of the caucy sequence 0, 0.9, 0.99, 0.999, 0.9999, 0.999999 etc..
And the limit of that sequence is trivially one.


Proofs based on manipulating fractions are quite useless, because the properly use them we have to show that 1/3 = 0.333333333~ or assume it as an axiom, but that's the basic property that we're trying to prove.


>>3 is also a flawed proof, before you can manipulate recurring decimals like that you first have to prove that you can treat them as normal numbers, which would involve defining them as a limit and proving simple limit laws like lim a + lim b = Lim a+b etc.

Name: Anonymous 2007-06-27 19:48 ID:y04j/M0y

>>15
Thanks for not bothering with the analytic proof, shithead.

Define a_n as the sequence a_n = sum(9/10^i) for i = 1 to n
Giving (0.9, 0.99, 0.999, ...), which approaches .9999... as n approaches infinity.

A sequence is said to converge to 'a' if for every epsilon > 0, there exists a natural number 'n' such that for all m > n, |a - a_m| < epsilon.

Clearly, |1 - a_n| = 10^-n

If epsilon is greater than or equal to 1, we can choose n = 1, since m > n implies
10^-m = |1 - a_m| < |1 - a_n| = 10^-1 < 1

If epsilon is less than 1, let l = floor(log_10(epsilon) - 1), n = abs(l) and m > n.
n > log_10(epsilon) since epsilon < 1 => log_10(epsilon) < 0

Since log_10(epsilon) < 0 < n < m, it can be said
log_10(epsilon) > -n > -m => 10^(log_10(epsilon)) = epsilon > 10^-n > 10^-m

So for epsilon less than 1, n = abs(floor(log_10(epsilon) - 1)), m > n => |1 - a_m| < epsilon

Since for every epsilon > 0 there exists an 'n' such that m > n => |1 - a_m| < epsilon, we can say that the sequence a_n converges to 1.

QED sluts

Name: Anonymous 2007-06-27 19:58 ID:/03AulS3

Proof that Gilgamesh=1

x = Gilgamesh
10x = Gilgamesh
10x-x = Gilgamesh - Gilgamesh
9x = Gilgamesh
Gilgamesh = 1 : Q.E.D.

Name: Anonymous 2007-06-27 20:38 ID:+ddmTCRZ

>>16


You really expect me to waste my time writing out that bullshit, especially on a computer, for people who wouldn't even know what I was on about?

I don't really get why you got so pissy about me not supplying the proof.

The convergence was trivial, I said that. To write it out is an exercise only people who needed practise using the definition of limits would do.

Thanks you for providing a useless proof though. Anyone who actually understands the concepts in my post could have written that proof out themselves.


Name: RedCream 2007-06-27 22:57 ID:HHEtpy1v

Well, #15/18, all I wanted to know was, what was the flaw in my simplistic, algebraic treatment of the matter.   Hence, I appreciated the response.

Others here should stick to what they know best ... which apparently involves fapping to artful drawings of shitting dicknipples.

Name: Anonymous 2007-06-27 23:00 ID:UpCvDXAy

mathematics is serious business.

Name: Anonymous 2007-06-28 19:17 ID:h1vmy1RY

Remember shitheads, numbers don't converge; functions can converge, but numbers don't.

Name: Anonymous 2007-06-29 0:43 ID:hcwfgrwT

Remember shithead, real numbers are limits of sequences; limits can converge.

Name: 4tran 2007-06-29 7:07 ID:Heaven

Good God, not another of these threads...  This subject has been beaten to death.  Stop already.

With regards to that rickroll thing, B&.

>>15
Your statements are true, and you provide a good introduction to real analysis, but it doesn't disprove >>10's claim that it's a limitation of our number system (real numbers).  The current definition of real numbers doesn't allow for infinitesimals, so we just say "infinitesimals = 0" (at least in this case) or something.  If we want infinitesimals and such, we can gb2 that nullity theory.

Name: Anonymous 2007-06-29 15:41 ID:hPuH7hdy

>>23


>>15 here.

Might just be me, but it seemed like you're just talking babble.

It's not a limitation of our number system, it's merely an anomaly that occurs due to how we define the real numbers. All it means is that all rational numbers instead of having a unique decimal expression, have two. And it's easily solved by just picking one of the two either .999....~ or 1.000~ and using it for every decimal expansion.

lol, looked up nullity theory, I assume that guy did it for the lulz.

Why do we want infinitesimals?
I don't see it as a limitation, just a property of the real numbers.

In fact the existence of a real "infinitesimal" I'm pretty certain would lead to all sorts of contradictions.

Name: Anonymous 2007-06-29 15:50 ID:Heaven

>>23
Nullity didn't have anything to do with infinitesimals, and infinitesimals do not make 0.999... != 1 in any meaningful non-standard model of the real numbers.

Name: Anonymous 2007-06-29 16:11 ID:hcwfgrwT

>>24
there aren't infiniteseimals in the reals, there are legitimite systems that have them, hyperreals or transreals or something, i've heard of them but never worked with them, I don't know, but it's not relevant to this.

anyway, anyone whos ever done real analysis can verify what 24 just said.  most books that discuss the reals in depth or construct the reals will have a proof of every rational number having two representations.  or more generally: that every real number has either one representation or it has two, one ending with repeated 0s and one ending with repeated 9s.

Name: Anonymous 2007-06-29 16:15 ID:hcwfgrwT

>>26
actually i take back the part about every rational number having two representations.  stop confusing me :D  1/3 for instance doesnt, its only .33333...  the "that every real number has either one representation or it has two, one ending with repeated 0s and one ending with repeated 9s. "  is right though.

Name: Anonymous 2007-06-30 1:31 ID:mFNtoyRk

>>27

Every real number has one representation: an equivalence class containing an uncountably infinite set of Cauchy sequences. It may also be representable as an integer, as an ordered pair of integers (rational number), ...

Name: Anonymous 2007-06-30 1:37 ID:5TBoSaFY

>>28

Sorry, I made another mistake, this is what I should have said, I promise, I'm looking at the proof right now.

"A real number x has exactly one decimal expansion or else x has two decimal expansions, one ending in a sequence of all 0s and one ending in a sequence of all 9s."

Name: 4tran 2007-06-30 2:47 ID:Heaven

>>24
I'm not well known for being easy to understand, so I'll try again.  First, limitations are not necessarily bad.  It's a limitation of the rational numbers that it doesn't include pi.  Pi is useful, so we create a new set of numbers, namely the real numbers, that does include it.  In this case, it's a limitation of the real numbers that "infinitesimals" are not included.  It's not that useful, so we usually neglect to construct a number system that does include "infinitesimals".  I don't remember the details, but I recall a qualified friend saying that including "infinitesimals" causes problems with open/closed sets.

>>25
gj - any model of the real numbers cannot include "infinitesimals"

Name: Anonymous 2007-06-30 22:43 ID:hmkTqqRl

>>30
any model of the real numbers cannot include "infinitesimals"
Why not? There's always 0.000...1 or 0.999...0, for example.

Name: Anonymous 2007-06-30 23:24 ID:Heaven

>>30
Nonstandard model of the real numbers means a model of the real numbers which does _not_ meet the _standard_ definition of real numbers. It's considerably more interesting than your idea of a nonstandard model, which is apparently one which is standard in every way.

>>31
Idiot.

Name: Anonymous 2007-07-01 1:53 ID:zGJlfcNK

>>31
.999...0 != .999...

Name: Anonymous 2007-07-01 8:44 ID:S++eUpHQ

>>33
Yes, that's why I said there are infinitessimal numbers such as 0.999...0 that fit the real numbers and can be easily expressed the way I did. Think of an infinite number of 9s, and right when you're about to reach infinity, you put a 0, and poof, you have a new number that's right before 0.999... (and two steps before 1).

Name: Anonymous 2007-07-01 9:23 ID:zGJlfcNK

>>34
But .999... is a real number since it is equal to the number 1.

Name: Anonymous 2007-07-01 9:46 ID:S++eUpHQ

>>35
How the fuck would .999... be equal to 1; it's a different number because it has an infinite number of NINES. It gets infinitely close to 1, but it's never 1 as it's made of NINES, not 1 dot 0.

Name: Anonymous 2007-07-01 11:07 ID:DWF09/nQ

>>36
The sequence (0.9, 0.99, 0.999, ...) converges to both 0.999... and 1. If a sequence converges to two values, those values must be equal.

Name: Anonymous 2007-07-01 11:33 ID:dohQ7Wrt

>>34

THAT MAKES NO SENSE YOU RETARD


God, I fucking hate it when people argue maths when they don't know shit.

This question has already been answered, not only in a million other threads, but in the thread as well if you morons would just read.

THERE ARE NO INFINITESIMALS IN THE REALS, that fact is very easy to prove, for every real number, r ,there is a natural number n such that 1/n < r.

If there wasn't then the naturals numbers would be bounded above, contradicting the axiom of archimedes.

However there doesn't exists any infinitesimals in the rationals trivially, and every real number is larger than a rational therefore there are no infinitesimals in the reals.


Oh and by the way 0.999......0 , if that even meant anything at all, is not an infinitesimal.

An infinitesimal would be 0.999..... - 0.999....0.

God, this thread is full of fail.

Name: Anonymous 2007-07-01 12:41 ID:S++eUpHQ

>>38
YHBT

Name: Anonymous 2007-07-01 16:06 ID:Heaven

>>38
we don't give a shit

Name: J355OP 2007-07-01 18:26 ID:1ui7+zkH

let 0.9(rec) = x
100x = 99.9(rec)
100x-x = 99
99x=99
x=1

0.9(rec) = 1

Name: 4tran 2007-07-01 22:41 ID:sx+D8fgs

>>38
"every real number is larger than a rational therefore there are no infinitesimals in the reals."

That doesn't make sense.  1 is a real number, and it is not greater than the rational number 2.  Even if it were true, it says nothing about infinitesimals.

For every real number, I can pick a smaller rational number.
For every rational number, I can pick a smaller real number.

The rest of what you said is true.

Name: Anonymous 2007-07-01 23:10 ID:VnyA+HZ5

>>42

Not "every real is larger than EVERY rational", dum-dum.

Name: 4tran 2007-07-01 23:27 ID:sx+D8fgs

"EVERY real number is larger than A rational therefore..."

I didn't quite interpret that correctly.  The statement is still false since such a rational does not exist.

Unless I'm still failing at interpreting, and he just means "For any real number R, there exists a rational number Q such that R > Q"

Name: Anonymous 2007-07-01 23:57 ID:0ZmSLVym

>>44

good work.

Name: Anonymous 2007-07-04 0:12 ID:8NbgOeeI

Idiot.

Lets put it more simply

99  1        (99 cant equal 1)
100 = 99
/////////////////
Above are your variable you must insert them in one "mathematical sentence" if you cant why dont you just do this simple equation

1 = 0 OH SHI- DOESNT WORK
1 = 0 +1 *fixed

Name: Anonymous 2007-07-04 0:21 ID:w6HO7DZE

>>46
making shit up

Name: Anonymous 2007-07-04 12:51 ID:Heaven

>>46
You need to learn english, math, and how not to be a fucking moron. In reverse order.

Name: Anonymous 2009-03-18 3:06

I feel the need, the need for weed!

Marijuana MUST be legalized.

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