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.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
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... = 1karplas said:snip
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.maninahat said:Yes, but that is where it deviates from real life.
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.The best way of knowing whether a number can be rational is whether it can be converted to a simple fraction.
Protip: Infinity minus 1 is still infinity, Subtraction does not make it a finite numberWinthrop 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...1Spencer Petersen said:x=.9999...
10x=9.9999...
10x-x=9.9999...-.9999...
9x=9
x=1
.9999...=x=1
.9999...=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
In the case of a continuous function (e.g this case) the limit is equal to the value.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.
If you're referring to the 1/3 = 0.(3) etc. proof, I would like to agree with a quote from Wikipedia:mps4li3n said:The proof is pretty simple, everyone with any math knowledge should understand it...karplas said:the experts are right and that one lacks the mathematical insight or knowledge required to fully comprehend the proof?
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...
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.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".
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 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... = 1karplas said:snip
Zukhramm said: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_1Winthrop 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.
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 said:In the case of a continuous function (e.g this case) the limit is equal to the value.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.
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?Kingsman said: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 said:In the case of a continuous function (e.g this case) the limit is equal to the value.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.
no, your calculator would have said it was 0.3333333, or 0.33333333333333 or 0.3333333333333333Zukhramm said: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.matt87_50 said:who the hell says 1/3 = 0.333...
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.Winthrop said: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_1Zukhramm 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.