ASKSAGE: Sage Q&A Forum - RSS feedhttps://ask.sagemath.org/questions/Q&A Forum for SageenCopyright Sage, 2010. Some rights reserved under creative commons license.Wed, 12 Feb 2014 12:07:25 +0100Limit of 1/x = infinty?https://ask.sagemath.org/question/11018/limit-of-1x-infinty/Hi,
I don't get why `limit(1/x, x = 0)` returns `infinity`.
Shouldn't it be undefined?
Interestingly, Mathematica also returns `infinity`, but on Wolfram Alpha it says two-sided limit does not exist.Wed, 12 Feb 2014 11:04:50 +0100https://ask.sagemath.org/question/11018/limit-of-1x-infinty/Answer by moroplogo for <p>Hi,</p>
<p>I don't get why <code>limit(1/x, x = 0)</code> returns <code>infinity</code>.</p>
<p>Shouldn't it be undefined?</p>
<p>Interestingly, Mathematica also returns <code>infinity</code>, but on Wolfram Alpha it says two-sided limit does not exist.</p>
https://ask.sagemath.org/question/11018/limit-of-1x-infinty/?answer=16035#post-id-16035Infinity is not signed
There also +Infinity and -Infinity .
example :
sage: limit(1/x, x=0)
Infinity
sage: limit(1/x, x=0, dir='+')
+Infinity
sage: limit(1/x, x=0, dir='-')
-Infinity
Look at here : [http://www.sagemath.org/doc/reference/calculus/sage/calculus/calculus.html](http://www.sagemath.org/doc/reference/calculus/sage/calculus/calculus.html)Wed, 12 Feb 2014 11:32:28 +0100https://ask.sagemath.org/question/11018/limit-of-1x-infinty/?answer=16035#post-id-16035Comment by Cassio for <p>Infinity is not signed
There also +Infinity and -Infinity .</p>
<p>example :</p>
<pre><code>sage: limit(1/x, x=0)
Infinity
sage: limit(1/x, x=0, dir='+')
+Infinity
sage: limit(1/x, x=0, dir='-')
-Infinity
</code></pre>
<p>Look at here : <a href="http://www.sagemath.org/doc/reference/calculus/sage/calculus/calculus.html">http://www.sagemath.org/doc/reference/calculus/sage/calculus/calculus.html</a></p>
https://ask.sagemath.org/question/11018/limit-of-1x-infinty/?comment=16276#post-id-16276Thanks. I get it now, although returning infinity when asking for the two-sided limit seems a bit misleading to me. But it's not just sage doing it...Wed, 12 Feb 2014 12:07:25 +0100https://ask.sagemath.org/question/11018/limit-of-1x-infinty/?comment=16276#post-id-16276