Poll: Does 0.999.. equal 1 ?

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Kingsman

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Anyone who says yes to this does not know basic Calculus.

The difference between the limit of something approaching x and the actual value of x REALLY matters at that level.
 

Spencer Petersen

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Ok take this logic

If you take the limit of y=(1/2)^x where x goes to infinity, you get 0

Logically, it wouldn't matter what fraction was inside the parentheses as long as it was between 1 and 0, y=(.1)^x would work equally as well

Is it not true that .1=.1^1? or .01=.1^2? or .001=.1^3?
Following this pattern, the decimal can be represented as .1^x where x is the number of zeros in between the final digit and the decimal point, minus 1

Now, if I gave you the number .(0)1, where its infinite zeros followed by 1, would it not be represented by the function .1^(∞-1)? Isn't ∞-1 the same as ∞ for the purposes of algebra? So it could also be represented as .1^∞.

Haven't we proven that in a case of finding the limit of y=(.1)^x where x goes to infinity the answer is always 0?

So logically, .(0)1=0.

Now, what is 1-.(0)1?
Wouldn't it be .(9)?
So, .(0)1=0,
1-.(0)1=.(9)
1-0=.(9)
1=.(9)
 

Zukhramm

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Winthrop said:
The flaw with this is that you have one less than infinity 9s after the decimal in 9.999 so it would not be 9 but 8.999...1
There's no such thing as "one less than infinity". Either it's infinitely many or there's finite number, which is followed by another finite number and not infinity.

There's yet to be a correct proof from someone who claims they're not the same, and multiple proofs from the ones saying they are. But I guess it's easy to argue you're correct if you ignore proofs.
 

Winthrop

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karplas said:
The proofs all use rounding errors. I personally know mathematicians who have proven those wrong. for instance 1/3 is not .33333 it is approximate. ((.99...)10)-.99.. = 8.99...1 not 9. I have not seen one of these proofs that does everything correctly. They need an approximation in the equation rather than an equals sign or it fails to be correct, and an approximation would not prove that .99... = 1
 
Feb 13, 2008
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maninahat said:
Yes, but that is where it deviates from real life.
Actually that is real life. If you're measuring distance up to an infinite point, you can't reach it. That's the point of infinite.
The best way of knowing whether a number can be rational is whether it can be converted to a simple fraction.
Remind me, what is 0.(9) as a fraction? Because 1/3*3 is 1. That's the point of decimalising fractions, or fractionalising decimals, you store the tolerance. Infinitely small measurements are treated as 0, but they still hold measure.

But then, repeated posts on a subject that has an official answer and a differing scientific answer are always good for post boosting. See the Triple Point of Water, How Many Moons does Earth have, Is Pluto a Planet and others.
 

rutger5000

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Lets give the number you mentioned X. Depends on situation, and of the order of magnitude of 1 - X (the number you gave). In most cases X equals 1 for all intends and purposes if 1 - X is somewhere in the order of magnitude of tenth to the minus 6 power. (1 divided by a million).
For Math, no it doesn't equal math and thats why math suck. Physics is better, and there it can equal one.
 

Spencer Petersen

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Winthrop said:
Spencer Petersen said:
x=.9999...
10x=9.9999...
10x-x=9.9999...-.9999...
9x=9
x=1
.9999...=x=1
.9999...=1
The flaw with this is that you have one less than infinity 9s after the decimal in 9.999 so it would not be 9 but 8.999...1

OT they are not equal. The reason they always appear to be is that the difference is so negligible that it can be ignored. You could say .999... ≈ 1 but that is because it is approximation. Also 1/3 does not equal .333... it is just a common approximation like pi ≈ 3.14
Protip: Infinity minus 1 is still infinity, Subtraction does not make it a finite number
 

Zukhramm

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Kingsman said:
Anyone who says yes to this does not know basic Calculus.

The difference between the limit of something approaching x and the actual value of x REALLY matters at that level.
In the case of a continuous function (e.g this case) the limit is equal to the value.
 

ultimateownage

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Feb 11, 2009
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I remember in the last post of this (There have been so fucking many) someone who actually understood maths pointed out how for the maths to work probably you must add a number to the end.
So 1.111... should be 1.111...1.
Even if it has no end, you have to assume it ends somewhere for it to work. Maths is not flawed, but the concept of infinity is.
 

karplas

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mps4li3n said:
karplas said:
the experts are right and that one lacks the mathematical insight or knowledge required to fully comprehend the proof?
The proof is pretty simple, everyone with any math knowledge should understand it...

The problem is that understanding it's real world justification is harder... way i see it is that because the 9 goes on for infinity it would take infinity for .(9) to be different from 1, and because infinity never ends it never is...

So yeah, magic...
If you're referring to the 1/3 = 0.(3) etc. proof, I would like to agree with a quote from Wikipedia:

William Byers argues that a student who agrees that 0.999... = 1 because of the above proofs, but hasn't resolved the ambiguity, doesn't really understand the equation. Fred Richman argues that the first argument "gets its force from the fact that most people have been indoctrinated to accept the first equation without thinking".
I'm in my first year of mathematics at university, so I can safely claim I have 'any math knowledge'. It doesn't make me a mathematician, but I've come to realise that many concepts we believe being trivially true actually are quite complex when mathematical rigor comes in.
 

Darth Crater

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Winthrop said:
karplas said:
The proofs all use rounding errors. I personally know mathematicians who have proven those wrong. for instance 1/3 is not .33333 it is approximate. ((.99...)10)-.99.. = 8.99...1 not 9. I have not seen one of these proofs that does everything correctly. They need an approximation in the equation rather than an equals sign or it fails to be correct, and an approximation would not prove that .99... = 1
How about my proof, then? If the two were different real numbers, by the density property, there would be an infinite number of other real numbers between them. No such numbers can be found. Thus, they must represent the same number.
 

Winthrop

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Zukhramm said:
Winthrop said:
There's no such thing as "one less than infinity". Either it's infinitely many or there's finite number, which is followed by another finite number and not infinity.
In both physics and math one less than infinity is a common term. And here are proofs they are not equal. Plus by definition .99999 does not equal one. http://en.wikipedia.org/wiki/User:ConMan/Proof_that_0.999..._does_not_equal_1
 

Kingsman

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Zukhramm said:
Kingsman said:
Anyone who says yes to this does not know basic Calculus.

The difference between the limit of something approaching x and the actual value of x REALLY matters at that level.
In the case of a continuous function (e.g this case) the limit is equal to the value.
If it's a CONTINUOUS function, yes, but he never made that distinction. I'm assuming it isn't continuous- in which case, it .999 etc. isn't 1.
 

Zukhramm

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Kingsman said:
Zukhramm said:
Kingsman said:
Anyone who says yes to this does not know basic Calculus.

The difference between the limit of something approaching x and the actual value of x REALLY matters at that level.
In the case of a continuous function (e.g this case) the limit is equal to the value.
If it's a CONTINUOUS function, yes, but he never made that distinction. I'm assuming it isn't continuous- in which case, it .999 etc. isn't 1.
You're asuming the function f(x)=x (because that's basically what we're talking about here, just a line of real numbers) is discontinuous?
 

mrscott137

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Apr 8, 2010
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Yes.
x=0.99... recurring.
100x=99.99... recurring.
100x-1x=99 so 99x=99
99x=99 divide all by 99.
x=1.
 

matt87_50

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Zukhramm said:
matt87_50 said:
who the hell says 1/3 = 0.333...
Who the hell doesn't? The was probably one of the first things I learned about math when I got my hands on a calculator as a small kid.
no, your calculator would have said it was 0.3333333, or 0.33333333333333 or 0.3333333333333333

depending on how many digits your screen could display, or the bit width of the calculators registers...

it didn't say it was 0.3recurring! just as it says 1, and not 0.9recurring!


the fact that 0.3333333333 'looks' a lot more like 0.3recurring, than 1 'looks' like 0.9recurring, doesn't mean anything!

as far as I'm concerned 1/3 = 0.3recurring should be no more or less questioned than 1 = 0.9recurring.

0.999 is closer to 1 than 0.33 is to 1/3
 

Darth Crater

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Winthrop said:
Zukhramm said:
There's no such thing as "one less than infinity". Either it's infinitely many or there's finite number, which is followed by another finite number and not infinity.
In both physics and math one less than infinity is a common term. And here are proofs they are not equal. Plus by definition .99999 does not equal one. http://en.wikipedia.org/wiki/User:ConMan/Proof_that_0.999..._does_not_equal_1
By definition, it does (0.9... anyway, not 0.9999). There cannot exist proofs both for and against the same thing, so the proofs at that link are necessarily false; sadly I don't have time to pick over them in detail.
 
Feb 13, 2008
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BTW, anyone attempting addition, multiplication, subtraction or division on a recurring decimal may just as well divide by zero.

That's an equivalency operation, and not a valid proof.