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mukushla
 3 years ago
Evaluate\[\lim_{x \rightarrow 0}x\lfloor \frac{1}{x} \rfloor\]
mukushla
 3 years ago
Evaluate\[\lim_{x \rightarrow 0}x\lfloor \frac{1}{x} \rfloor\]

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MarcLeclair
 3 years ago
Best ResponseYou've already chosen the best response.0It does not exist ax you can't factor anything out and will end up with 0/0.Which is an undetermined form. I hope I helped :/

MarcLeclair
 3 years ago
Best ResponseYou've already chosen the best response.0I am taking Cal 1 too single variable. I just went over that, :) ( ironically I was struggling with a question like that yesterday)

datanewb
 3 years ago
Best ResponseYou've already chosen the best response.0Well, the equation is not defined at x=0, but as x approaches zero, would it's limit not be 1? @MarcLeclair, do you take the same stance for \[\lim_{x\rightarrow \infty}x\lfloor \frac{1}{x} \rfloor\]

MarcLeclair
 3 years ago
Best ResponseYou've already chosen the best response.0I think that limit would then be infinity ( positive infinity) . However, I do not know why this sounds wrong to me, it is really puzzling my brain. As for his equation, it is because you will ALWAYS end up 0/0 which Doest not exist. Unless there is another way to define it ?

hellow
 3 years ago
Best ResponseYou've already chosen the best response.1As for the second question, we have \[ \lim_{x \rightarrow \infty } x \lfloor \frac{ 1 }{ x } \rfloor = 0\], because, as long as x>1, \[\lfloor \frac{ 1 }{ x } \rfloor = 0\] You can make x as large as you like and this will still be true. Therefore, the product \[x \lfloor \frac{ 1 }{ x } \rfloor\] must also be zero, no matter how large x becomes. In other words, the product is not getting closer and closer to 1, it is consistently zero, i.e. {0,0,0,...}. As for the first question, I think\[ \lim_{x \rightarrow 0} x \lfloor \frac{ 1 }{ x } \rfloor \] does not exist. For any x=1/n, the value will be 1. For instance \[1/4\lfloor \frac{ 1 }{ \frac{ 1 }{ 4 } } \rfloor = 1/4\lfloor 4 \rfloor = \frac{ 1 }{ 4 }4 = 1\]. However, as x gets closer to zero, is the limit approaching 1?

mukushla
 3 years ago
Best ResponseYou've already chosen the best response.2Hint : for all \(x\in \mathbb{R}\)\[0\le x\lfloor x \rfloor<1\]

mukushla
 3 years ago
Best ResponseYou've already chosen the best response.2it has to do something with squeeze theorem

hellow
 3 years ago
Best ResponseYou've already chosen the best response.1I would probably try an epsilondelta proof if you are comfortable with those. The squeeze theorem is probably easier, but I don't see right now how it would work. For an epsilondelta proof, if you want your product to be less than some epsilon, choose some 1/n which is less than epsilon. Then choose x= <1/(n+1). That way you product could be n/(n+1), which would put you within a distance of 1/(n+1) from 1 (close enough). And if x is smaller than 1/(n+1), you would have to show that you would still be within a distance 1/n from 1. The details might be annoying, and there is probably a better way, I just don't see it!

mukushla
 3 years ago
Best ResponseYou've already chosen the best response.2thank u for ur effort :)

mukushla
 3 years ago
Best ResponseYou've already chosen the best response.2\[0\le \frac{1}{x}\lfloor \frac{1}{x} \rfloor<1\]\[\frac{1}{x}\le \lfloor \frac{1}{x} \rfloor<1\frac{1}{x}\]we're doin limit so x will not reach 0 so multiply both sides of later thing by x\[1\le x\lfloor \frac{1}{x} \rfloor<x1\]multiply by 1\[1x< x\lfloor \frac{1}{x} \rfloor\le 1\]apply limit\[\lim_{x \rightarrow 0}(1x)< \lim_{x \rightarrow 0}(x\lfloor \frac{1}{x} \rfloor)\le \lim_{x \rightarrow 0}1\]\[1< \lim_{x \rightarrow 0}(x\lfloor \frac{1}{x} \rfloor)\le 1\]so\[\lim_{x \rightarrow 0}x\lfloor \frac{1}{x} \rfloor=1\]

hellow
 3 years ago
Best ResponseYou've already chosen the best response.1Nice! I think that works, and am glad to see how to do it:).
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