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0.9 repeating = 1?
I was googling around today and i came across something rather odd. http://en.wikipedia.org/wiki/0.999.... Now, this wikipidia page claims that .99999 repeating = 1.
Here is a quick algebraic proof to support this, Quote:
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Re: 0.9 repeating = 1?
What is the difference between .9 repeating and 1?
Hint: a point. Now whats the dimension of a point? |
Re: 0.9 repeating = 1?
When you get to calculus they'll have you prove that .9999=1 using geometric series.
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Re: 0.9 repeating = 1?
I like this method. between any 2 different real numbers, there is at least one number between them not equal to either of them.
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Re: 0.9 repeating = 1?
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http://en.wikipedia.org/wiki/Geometric_series Consider .9~ to have a seed value of .9 with a ratio of .1. Use the formula proven on the wiki page. Voila! They also do an example problem under Repeated Decimals. :) |
Re: 0.9 repeating = 1?
I actually figured out that same proof in the Wikipedia article earlier this school year before reading about it. But 0.99 repeating does equal one. There is enough proof, and even common sense, as 1-0.999... =0.000... which is just 0.
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Re: 0.9 repeating = 1?
You'd be surprised how many people argue that "it can't be true". But it is. The key word is "repeating".
Now for the extra credit: What's the name of that line that goes over the last digit to indicate that it repeats infinitely? Spoiler for The Answer:
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Re: 0.9 repeating = 1?
Then I guess this means that (lim x-> 1-) is NOT 0.999~ :p
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By the way, after a certain point, it won't matter; your machinist won't go to that tight of a tolerance...:p |
Re: 0.9 repeating = 1?
Your wrong. 1/3 = 0.33333333333333333. an infinite amount of 3's. Not 0.33. So multiple .33333~*3 = .99999~, Not 1.
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Re: 0.9 repeating = 1?
Just for curiosity, what would happen if you approached the problem backwards, starting at 1, then subtracting:
1 - .1 = .9 1 - .01 = .99 1 -.001 = .999 ... 1 - 10^-n = .9~ as n approaches infinity You could argue the 10^(-infinity) approaches 0 and thus 1 = .9~ But then again, the equivalent expression, 1/10^n divides the number 1 into smaller and smaller parts. Just because the parts are smaller doesn't mean they are nonexistent. To me, this expression states that you can always divide 1 into smaller parts, therefore you can never really "reach" infinity, and therefore never "reach" .9~ It's just like 1/x . What happens as x --> infinity? "The limit is 0." Yes, but does the function itself every EQUAL 0? It gets closer to it, and closer, and closer, .01 .001 .00001 .00000000000000000000001 But there's always that 1 at the end, no matter how many zeros you throw in there. And you can't really put in "an infinite" amount of zeros in between, because then the 1 would be coming after "infinity" which nulls its definition. I may be wrong, but at least presents an argument different from the standard 1/3 stuff. |
Re: 0.9 repeating = 1?
I agree that .9~=1 if .3~=1/3. I just think it'd be more accurate to say that both are extremely close approximations. Though most mathemeticians will disagree with me.
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Re: 0.9 repeating = 1?
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