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**Tiberius** · (This post was last modified: February 21, 2013 at 9:25 am by Tiberius.)

(February 21, 2013 at 8:58 am)pocaracas Wrote: There are some infinities greater than other infinities.
#N < #R

True in the sense that some are "countable" and others are not. However, in the sense you used it in, the infinities are the same, since you are using the same variable (x).

pocaracas · February 21, 2013 at 9:51 am

aye, but even in non-countable infinities, there must be some that are greater than others.
∞/∞ is always indeterminate, according to what I learned in the Uni, some years ago....

**Tiberius** · February 21, 2013 at 3:49 pm

Right, my issue isn't with that. It's with your use of the lim() function, which deals with limits and not static equations.

∞/∞ makes no sense given that infinities are not actual numbers.

In your examples, you are never actually setting either the numerator or the denominator to infinity at any point. You are merely saying that as the value of 'x' approaches infinity, the equation (using x) approaches a constant.

pocaracas · February 21, 2013 at 5:23 pm

Yes, limits do behave like that... darn things, always messing with poor students' heads. Wink

LastPoet · February 21, 2013 at 5:32 pm

Infinities tend to mess with our heads. Best way to do math is a plain sketchbook and use it. My math analisys book author says in the preface: "you can't learn math without doing math".

Venom7513 · April 30, 2013 at 10:06 am

(February 20, 2013 at 3:10 pm)pocaracas Wrote: I always thought that x-dx != x, but you guys seem to be onto something.... .... ....
It seems dx is much larger than 0.000(etc)1.

PS: x is a real number; dx is an infinitesimal part of x.
!= means "not equals"

Umm... No. Actually,
$[Image: gif.latex?\LARGE%20d[f(x)]%20=%20\lim_{h...(x)-f(x-h)]$

That's how we get...
$[Image: gif.latex?\LARGE%20\frac{d[f(x)]}{dx}%20...f(x-h)}{h}]$

dx isn't a number. d is an operator that maps functions to functions. The ratios of these functions produce the derivative.

And for the record...
$[Image: gif.latex?\large%200.\overline{0}1%20=%2...n}%20=%200]$

**Mister Agenda** · April 30, 2013 at 12:17 pm

To make this about me, one of the little bitternesses of my life is that I graduated college with a GPA of 3.69 (repeating nine) when I needed a 3.70 for magna cum laude. One more correct answer on one test, or the prof in that class grading on a curve, and I would have had it! For some reason, pointing out that there's no real mathematical difference between the two GPAs didn't help. Angel

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