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#251
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1/2 < 9/10 3/4 < 99/100 7/8 < 999/1000 15/16 < 9999/10000 It would be very odd if the limit of the first were greater than the limit of the second, since it can never overtake it. (But it's not odd that they have the same limit.) |
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#252
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Most especially for this: "Any limit notation is necessary because we don't have the tools to deal directly with infinities" |
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#253
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That's very kind, but I'll be happier if this all seems to be a little more real a little less like some sleazy math trick to you.
Yes? No? Last edited by allotrope; 08-06-2012 at 05:44 AM. |
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#254
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The value of .999... at infinity is .999... or if you prefer 1 - 1/infinity. Yes I realize 1/infinity is undefined, and no I can;t precisely definie it. But someone shoudl get busy on it ;-)
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#255
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(1) the ordinary rules of arithmetic, and (2) the fact that the sum of two real numbers and half of a real number are real numbers themselves. Limits are quite irrelevant. From that, if x<y then x<(x+y)/2<y, i.e., (x+y)/2 is a real number between x and y not equal to either. It's a bit harder to prove that between any two real numbers there is a rational number, but that theorem isn't really relevant here. |
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#256
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I mean that if you can show me how .999... = 1 without limits I will be very happy! |
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#257
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what ordinary rules of arithmetic? I am not sure how 2) applys here? Last edited by erik150x; 08-06-2012 at 05:51 AM. |
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#258
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But I'm guessing your response will be something along the lines of even at infinity there will still be an infinitely small difference. Except, at infinity, no, even that infinitely small difference has been gobbled up by all of those repeating 9's. You have gone out to infinity such that there is no end to the decimal where you could find that infinitesimal difference. It's gone, buried in infinity. Sorry, but that's about the best I can do by way of an explanation. Last edited by allotrope; 08-06-2012 at 05:55 AM. |
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#259
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#260
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#261
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Instead of asking "limits" to "explain" or "understand" infinity. We only ask that limits be a usable tool for "working with" infinity. This is much more reasonable goal! As a comparison, consider something as basic as a line mathematics. Most of us just "accept" this mathematical idea of a "line" without giving it a lot of thought. But what exactly is a line? Can we construct it? Is a piece of string drawn pull tight like a guitar string a "line"? No, that doesn't meet the definition of a line. How about a thin laser beam? Nope. Even a line that is the width of 1 electron is not a true "line" in the the mathematical sense. A mathematical line has zero width. If we say a line is is a set of infinite points with zero width, how can we even create statements such as "2 parallel lines never meet" ... the non-mathematical mind can retort, "well sure, 2 of impossible and incomprehensible items of zero width never meet, duh!" Imagine a inquisitive child trying to drill down this line of reasoning to its very end. You must explain that it's not possible to "think" of lines like that because it leads to writing English sentences that are meaningless. If we can't even construct lines, how do we comprehend it on some satisfying metaphysical sense? We don't. A line is simply an idea we work with. (Same as limits.) Another example... on a piece of paper, we can write the number 1 x 1081 which is a number larger than the number of atoms in the universe. This number is incomprehensible. Even with that difficulty, how can we claim: (1 x 1081 + 1) > (1 x 1081) It's only the rules of addition that says that's statement is true. We can't arrange a pile of 1 x 1081 apples (or atoms) and visually see that one heap is obviously 1 bigger than the other. If we can accept mathematical definitions of "lines" and rules of addition on incomprehensibly large numbers, we can also accept the concept of "limits" and that .999... = 1. |
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#262
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For there to be a difference, you need to be able to subtract your decimal from 1 - correct? Now, in order for you to do that, don't you have to be able to find the tail end of the decimal? But at infinity, there is no tail end because . . . wait for it . . . you're AT infinity. Are you feelin' any love yet? |
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#263
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Between Giles and Allotrope they make a compelling case as to why intuitvely I should expect .999... to eqaul 1. But Limit theory just is less than satisfying. It says nothing about how or why... just that it does. It leaves me thinking perhaps .999... does = 1. Yet it seems such a fundimental issue, that the fact we have no proof troubles me. To me limits hide our ignorance in this matter.
As Allotrope says "It's gone, buried in infinity" -- okay maybe it is, but thats to me as vague as 1/infinity. |
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#264
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So thats not a fair compairison to the assumptions of Limits. |
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#265
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Last edited by erik150x; 08-06-2012 at 06:27 AM. |
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#266
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I was using the subtraction example to make it feel more concrete. But the point really is that to find that tiny difference you have to keep hopping from one 9 to the next ad infinitum. Therefore, if you can never actually FIND the difference, no difference exists. |
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#267
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Okay you guys have worn me down for now. I have to try and get an hour or so of sleep before work. :-(
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#268
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So how do you "accept" the mathematical concept of a 1-dimensional line with zero width?
Last edited by Ruminator; 08-06-2012 at 06:34 AM. |
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#269
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I think 1 + 1 = 2 before we ever convcieved of a number. Last edited by erik150x; 08-06-2012 at 06:36 AM. |
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#270
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You tell me what a line is. Last edited by erik150x; 08-06-2012 at 06:42 AM. |
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#271
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Pls re-read what I said if that's really what you believe. |
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#272
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Let's divide 1 by 9: **0.111111111.....1 **_______________ 9/ 1.0000000000....0 *-0 **10 **-9 ***10 ***-9 ****1 *******etc. *************10 *************-9 **************1 STOP!! I (erik150) will arbitrarily stop here and discard the remainder so that I can have the result end with a 1. This is also why my (erik150's) intuition is skeptical that 0.333... is equal to 1/3, since the removal of the remainder necessarily makes 1/3 > 0.333... (or rather, 1/3 > 0.333...3)! erik150, you really need to understand that there is NO END to the number of decimal places to the right of the decimal point. It's like saying "infinity" is just some humongous finite number that you simply stopped bothering to count. I mean, what's stopping me from just going one more step in the above division? Why the stopping point? |
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#273
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Proof Limit Definiton Contradticts Itself...?
Ok first I haven't read any posts since my last. I have been trying to sleep. But I had to post this while it's in my mind.
Let's assume Limit Theory is correct. .999 = 1 And for that matter 1/2 + 1/4 + 1/8 + ... = 1 Now picture 2 horizontial parrallel line segements, A and B. A direclty above B. for fun lets say these lines are a mile long (it doesn't really matter) Each line segment is labeled A1 and B1 on the left most point Each line segment is labeled A2 and B2 on the right most point We can divide a line segment into an infinite number of points right? So we do this for both lines. Making sure each point on the top line, lines up with the bottom line. On the top line I will lablel each point as follows 1 . 0 0 0 . . . On the bottom line I will label each point as follows 0. 9 9 9 . . . How can I do this? Right how can I label 2 infinite lines? Well to make things simple let's assume I am marking line A with my left hand and line B with my right. So I only have to make one pass. And I will only decribe marking line A, but it assumed I am marking line B at each point as well. I make my first mark at the half mile point, and put (1.). then at the 3/4 mile mark 0, then at the 7/8 mile mark 0, then at the 15/16 mile mark 0, etc... Each mark takes me 1/2 the time to get to since I am traveling half the distance each time. So lets say it takes me 30 mins to get to the first mark then 15 mins to get to the second mark, 7 mins 30 secs for the 3rd and so on. I think most can see where I am going with this, but I will go on... According to limit theory I can travel to the end in 1 hour marking an infinite number of points. 1/2 HOUR + 1/4 HOUR + 1/8 HOUR + ... = 1 HOUR And that consists of an infinite number of points. Now I have my lines both labeled. To review as such: On the top line I will lablel each point as follows 1 . 0 0 0 . . . On the bottom line I will label each point as follows 0. 9 9 9 . . Can I really physycally do this? Of course not, but this is just a thought experiment so bear with me. I ceartainly can walk a mile in one hour and one could certainly imagine two lines with these points exisintg as they do on lines. Furthermore whether I actually labled them or not, does it really matter? The point is I can get to them and pass them all in 1 hour easily. Now we reverse the process and start subtracting line B from A. To be honest do we really need to finish the whole calculation? Because once we see the 0 at the end of line A and the 9 at the end of line B, we know what the result will be: .000...1 So it seems we can in a theoretical way find the end of these numbers and do the math. But the math contradicts what limit theory tells us the answer should be which would be: .000...0 I guess this is all a fanciful way of saying it in the land of math we can get to the end of the line as sure as we can walk across the room. Calculating an infinite number of decimal places is a snap. I could be deleriously tired, but it makes sense to me. |
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#274
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Maybe we are just not connecting with each other here. I don't know why there is need to bring the construction of reals or divison into this? We were simply tlaking about adding already existing numbers. Namely .999... and 10 of them. |
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#275
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You know dude, if you just don't WANT to understand, that's fine, but at least be honest about it, m'kay? |
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#276
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As we discussed before to get from point A to point B, you must go half way 1st right? And 1/2 of the remaining distance and so on... this is the classic Zeno's paradox which is solved by saying 1/2 + 1/4 + 1/8 + ... = 1 is it not? Is there not an infinite number of steps involved there? Do we clearly not move across the room form point A ot point B? Is there theoretically not an infinit number of points there? Do I really have to label them? All i need to do is reach the last one, labeling them is not really neccessary. We have reached the end of an infinite number of points stecteched along this mile line line segment. We already know how they should be labeled, do we not? Do you susggest at some point in this process I would (if I was actually marking them), stop marking zero's on top or stop marking nine's on the bottom? The point is we can find the end of an infinite number of points, and that's all we really need to do here. I'm not trying to not understand? Please tell me where my logic is wrong here? |
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#277
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Usually I would think it meant not more than countably many, which does not mean not an infinite number, so I don't know what you are on about.
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#278
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It's not that the equation of .999... with 1 is "built in" to the system we use as an "assumption." Rather, it's a logical result of the definitions used at the foundation of that system. You can prove it--using the assumptions we all use when we use the decimal number system.
And it is in fact true, in the sense that in the system we are using when we use the decimal number system, the quantity represented by the expression ".999..." is the very same quantity as that represented by the expression "1". Maybe you already know both of those things, but you've said things lately which seem to indicate you think otherwise so I want to be sure this is clear. In a system wherein .999... =/= 1, the expression ".999..." does not represent the same quantity that the expression ".999..." represents in the normal decimal number system. It represents some other quantity. (In fact, it may not represent a "quantity" at all in the colloquial sense. It depends on the model.) I think. |
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#279
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Let's put a little '9' at each halfway mark. There will still be an infinite number of them. As I said before, YOU NEVER GET TO POINT B EXCEPT AT INFINITY. It's not my fault if you don't read my posts now is it? |
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#280
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I don't know a lot of maths, but your explanation is concise, and I don't find much to argue about here. When .999... is used, it's used in place of 1. It indicates to me that a faulty algorithm that results in an endless loop, producing 9's forever, but the value it's trying to produce is 1. As far as .999....1 goes, it's pretty easy to understand that there are an infinite number of numbers between 1 and 2, yet 2 still follows 1. I don't know what to do with .999...1, but it doesn't seem difficult to understand. |
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#281
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Do I not pass an infinite number of 0s on top and 9s on the bottom by time I reach the end of the line. Each half way point represents a number on top and bottom. 1/2 + 1/4 + 1/8 +... + 1/infinity = 1 This is the classic Limit soultion to Zeno's paradox? Is there not an infinite number of points here? Please tell me where the logic is wrong? |
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#282
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#283
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This is an infinite series represented by 1/2 + 1/4 + 1/8 + ... + 1/infinity = 1 In both distance and time I have taveled: I have reached an infinite number of points, yes or no? |
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#284
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There is no last numeral.
Last edited by TATG; 08-06-2012 at 09:32 AM. |
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#285
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You said:
Your logic is flawed because you still fail to understand what infinity means. -- this is a useless counter, means nothing... except your opinon of my knowledge. Nothing about the actual logic I stated. Let's put a little '9' at each halfway mark. There will still be an infinite number of them. As I said before, YOU NEVER GET TO POINT B EXCEPT AT INFINITY. --- How did I not reach an infinite number of points on my walk? It's not my fault if you don't read my posts now is it? -- again usless counter statement. |
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#286
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Are you labeling a point each time? I'll assume yes. In that case, it will take you an infinite amount of time and you will hit an infinite number of points. You will still never reach point B except at infinity. Is that better? |
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#287
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But I Just told you how to find the last numeral. Please tell me how I my method is wrong?
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#288
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You are solving Zeno by appealing to motion in the physical world - yet you are claiming that you physically were able to generate the labelled points - and you do have to label them all because you claim that the "last" point is the one that matters. You are thus confusing together an appeal to physical motion with an infinite process. But you need to provide a solution to Zeno in the abstract that allows your labelling to work. Placing the intervals in a one to one relationship with the fractions of time needed to label them is the usual solution - but you need to then show that time reaches the end - thus you are trying to prove something by assuming its converse. Why should the time fractions reach the end point and not the fractional distances? Either place both or neither in the physical world - you can't place one in the physical and the other in the abstract.
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#289
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Last edited by erik150x; 08-06-2012 at 09:36 AM. |
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#290
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Last edited by allotrope; 08-06-2012 at 09:38 AM. |
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#291
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And with an infinite number of them BY DEFINITION there is no LAST ONE.
Last edited by allotrope; 08-06-2012 at 09:39 AM. |
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#292
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#293
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Again, there is no need to physically label them, why should there be? |
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#294
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#295
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You can't really be this thick. I don't mean to be rude but that is just too over the top. |
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#296
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Since the distince is infinitely divisible in halves, you must pass or reach an infinite number of them no? |
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#297
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YOU NEVER GET TO B - you only get there at infinity. |
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#298
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So you can't move? Thats shame. I am sorry you can never get from pont A to point B? Your whole life must be an illusion?
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#299
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You continue to move but in every smaller increments. When the number of increments reach infinity, you arrive at point B.
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#300
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Thank you. So we agree as I moved from the start of my walk to the end, I did indeed reach an infinit number of points each 1/2 the distance of the previous?
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