Search All of the Math Forum:

Views expressed in these public forums are not endorsed by NCTM or The Math Forum.

Notice: We are no longer accepting new posts, but the forums will continue to be readable.

Topic: How does infinitesimal exist?
Replies: 21   Last Post: Jun 7, 2013 12:13 AM

 Messages: [ Previous | Next ]
 Angela Richardson Posts: 42 From: UK Registered: 6/22/11
Re: RE: How does infinitesimal exist?
Posted: May 1, 2013 9:49 AM
 att1.html (1.9 K)

The intersection of the rationals in (0,1) and (0.5,7.5) is just the set of rationals in (0.5,7.5), unless I have misunderstood the question.

There are aleph-naught rationals in any interval which contains 2 rationals (e.g. is not (1,1) or [2,2] ). The rationals in the finite interval (a,b) can be placed into a bijection with the natural numbers by counting the integers by listing all multiples of 1 in (a,b) in increasing order, then all the multiples of 1/2 that are not already in the list, then multiples  of 1/3 etc.

________________________________
From: mathCurious <discussions@mathforum.org>
To: discretemath@mathforum.org
Sent: Wednesday, May 1, 2013 9:09 AM
Subject: Re: RE: How does infinitesimal exist?

Specifically what is right? I am saying that if I am interpreting all this correctly (I am not positive on this point, hence I am posting here to ask) you end up finding an infinity that is less than aleph-naught, which contradicts what I interpret this article (http://en.wikipedia.org/wiki/Aleph_number) to be saying when it says that aleph-naught is the smallest infinite cardinal.  Hence I am confused.  Am I making some error here?  BTW, I know who Cantor is.  Thanks again for answering.

Date Subject Author
3/4/13 Taber McFarlin
3/5/13 Peter Scales
5/1/13 alax wilson
3/5/13 Taber McFarlin
3/5/13 Peter Scales
3/6/13 grei
4/11/13 grei
4/29/13 mathCurious
4/29/13 mathCurious
4/29/13 mathCurious
4/29/13 Ben Brink
4/30/13 mathCurious
5/1/13 Ben Brink
5/1/13 mathCurious
5/1/13 Angela Richardson
5/1/13 mathCurious
5/2/13 mathCurious
5/3/13 Ben Brink
5/3/13 mathCurious
5/4/13 Angela Richardson
5/4/13 mathCurious
6/7/13 grei