Login

**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

Login
Username:
Password:	Lost Password?
	Remember me

Possibly Related Threads...
Thread		Author	Replies	Views	Last Post
	Is zero a natural number?	Jehanne	81	9713	July 16, 2023 at 7:29 am Last Post: Angrboda
	Question for finitists -- 0.999... = 1?	Jehanne	23	4375	November 26, 2022 at 8:40 pm Last Post: Jehanne
	Dividing by zero	Tea Earl Grey Hot	77	24060	January 18, 2015 at 12:31 am Last Post: GrandizerII
	Maths proves 1=0.999.. thus ends in self contradiction	shakuntala	11	6408	December 21, 2014 at 3:57 pm Last Post: Thumpalumpacus
	What is Zero (0)?	ManMachine	22	8124	February 9, 2014 at 11:11 am Last Post: truthBtold
	[split] 0.999... equals 1	Rhizomorph13	330	113711	February 20, 2013 at 6:47 am Last Post: Categories+Sheaves
	Why is infinity afraid of zero?	Rayaan	38	18017	June 28, 2012 at 12:50 pm Last Post: Opsnyder
	If 0.999 (etc.) = 1, does 1 - 0.999 = 0?	Child of Stardust	16	11529	March 6, 2012 at 2:12 pm Last Post: Child of Stardust
	The probability of the accuracy of probability itself? Etc.	Edwardo Piet	15	6840	February 9, 2009 at 1:54 pm Last Post: chatpilot