Talk:Number line

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Contents 1 n(R) equal to Aleph 0? 2 Other stuff 3 "All of the real numbers from negative infinity to positive infinity" 4 Division as repeated subtraction?

[edit] n(R) equal to Aleph 0?

Now it seems that the number line is, in essence, the set of the reals. The cardinality of the set of the reals is NOT the "simplest and smallest measure of infinity" or whatever - or at least, I thought it wasn't. I thought that the simplest and smallest degree of infinity was the cardinality of the natural numbers (equal to n(Z) and n(Q)). Am I correct? I will change it, and if I'm wrong, someone else will change it back. 61.9.204.168 08:23, 15 September 2006 (UTC)

[edit] Other stuff

From my textbooks, a number line should have only one arrow, marking the direction of the possitive numbers; not two arrows. —The preceding unsigned comment was added by Yazewu (talk • contribs) 02:28, 8 January 2006.

That's an uncommon convention, but you're welcome to add it to the article, if you cite the reference! Melchoir 01:19, 9 March 2006 (UTC)

I have also seen this convention used - on a cartesian line or plane, the arrows indicate the direction of positive. However, the convention referred to in the article is simply that of the line continuing to infinity, in which case it should be present on both the left and right ends of the line.

61.9.204.168 08:25, 15 September 2006 (UTC)

Can the number line be curved so that +infinity and -infinity meet?

homagni@vsnl.net

Take a look at the real projective line, which joins the real numbers with an unsigned infinity. As far as practical/useful/meaningful constructions, this probably comes as close as possible to what you want to describe.02:47, 18 October 2007 (UTC) —Preceding unsigned comment added by 74.129.252.81 (talk)

[edit] "All of the real numbers from negative infinity to positive infinity"

Is that accurate? It seems prone to produce confusions about infinity - infinity isn't in the set of reals, and I don't think infinity can reasonably be placed on a line with the reals (what number would it come after?). Can we just say "all the real numbers" and leave infinity out of it? VoluntarySlave 03:16, 31 January 2007 (UTC)

[edit] Division as repeated subtraction?

From the article: "It is used sometimes to teach multiplication as repeated addition, and division as repeated subtraction." Division is not repeated subtraction. I'll remove this; re-add if you disagree. 03:00, 18 October 2007 (UTC)