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PlanetMath is a virtual community which aims to help make mathematical knowledge more accessible. PlanetMath's content is created collaboratively: the main feature is the mathematics encyclopedia with entries written and reviewed by members. The entries are contributed under the terms of the Creative Commons By/Share-Alike License in order to preserve the rights of authors, readers and other content creators in a sensible way. We use LaTeX, the lingua franca of the worldwide mathematical community. On February 13th 2013, PlanetMath.org was updated to use the new software system Planetary. Some release notes are here. Please report bugs in the Planetary Bugs Forum or on Github.

## Latest Messages

Dec 11
$${\displaystyle \intop_{\lambda_{1}}^{\lambda_{2}}}\phi(\lambda)\, d\lambda$$ ?? or $${\displaystyle \intop_{\lambda_{1}}^{\lambda_{2}}}\phi\, d\lambda$$ Answering that should answer your equestion. BTW: Try the program Lyx; it's an easy way into Latex and these symbols. Easy on-ramp and good road afterwards :)

Dec 11
Let P1=P2=S1=S2=2 (P1+P2)/(S1+S2)=1=((P1/S1)+(P2/S2))/2 I presume that your relationship symbol meant: not equal. Ray

[p] 1/0 by rrogers Dec 11
I have seldom seen anything good coming out of division by zero.

Dec 11
In general it has been more usefull, more extensible, to define "rational numbers" as a pair (a,b) with a multiplication and addition rule. And then take Integers as an example. Addition rule (a,b)+(c,d)~(a*d+b*c,b*d) Multiplication rule: (a,b)*(c,d)~(a*c,b*d) a,b,c,d \in Z and b,d != 0 Definitions like this allow one to manipulate items from a more general ring and also use the usuall nomeclature a/b=c/d . This includes certain exotic cases in Algebraic Geometry.

/0 by eipi10 Dec 7
Whenever I evaluate the inverse of Euler's Identity I get infinity. However when taking the inverse of 0 I do get a value only described as undefined. Can someone elaborate on this?>

Dec 4
I withdraw my remark I made on dec. 3. It was ment for rational points of finite order.

Dec 3
The solution is quicker obtained by using Nagell-Lutz's theorem

Dec 1
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Nov 29
Sorry, my correction should read Two instances of ”$< c - δ$” should be replaced by ”$> c - δ$” for the proof to make sense.

Nov 19
I think I have a greater understanding of a tetrahedron now, your explanation was simple enough. I was thinking of studying mathematics at university, but instead opted to go into computing, repair diagnostics, <a href="http://www.compuchenna.co.uk/how-to-back-up-files/">sys backup & recovery</a> etc... which has turned out to be most helpful for me, at least.

Nov 18
Hi Planetmath, I have been doing some research on Brun's constant, and it seems the value that is converged to is 1.902160583104...Is there not a zero after the 9 ie 1.902? I saw 1.92 on the actual page that discusses Brun's constant. I just joined the site and would like to say this is one cool math site! Just wanted to check on the 1.902 vs. 1.92 Thanks, twinprime57

Nov 11
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Nov 8
The last verctor w3 is incorrect it should be (1856/1129,-3132/1129,-1392/1129) get the modifications done if possible

Nov 8
my post got malformed after pressing post button