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cannot calculate limit

asked 2015-01-30 04:20:28 -0600

marguin gravatar image

updated 2015-01-30 06:08:09 -0600

tmonteil gravatar image

No answer from Sage-6.4.1 for this limit :

var('n'); u = (1+sqrt(n))^(-n); limit(u(n=n+1)/u,n=infinity)

Sage 4.7 gives 0 (correct). Why ?

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rws gravatar imagerws ( 2015-02-01 02:41:48 -0600 )edit

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answered 2015-01-30 06:05:31 -0600

tmonteil gravatar image

updated 2015-01-30 06:07:48 -0600

I do not know exactly why, probably a regression in maxima. If you really want to know, you should provide a smaller interval of versions than (4.7, 6.4.1) so that we can have a look at the guilty commit. That said, you can still ask sympy to do that:

sage: limit(u(n=n+1)/u,n=infinity, algorithm="sympy")
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Thanks ! Note that converting to exponentials works. My best interval is (4.7, 5.8), sorry

marguin gravatar imagemarguin ( 2015-01-30 06:52:04 -0600 )edit

This does not evaluate (returns the question) in 5.2. So it's been a while. Thierry, maybe you can isolate the Maxima command and report upstream?

kcrisman gravatar imagekcrisman ( 2015-01-30 08:00:35 -0600 )edit

I never used maxima commands (nor maxima itself), but if you give me some hints me how to do that, i will be glad to.work on it.

tmonteil gravatar imagetmonteil ( 2015-02-01 11:10:51 -0600 )edit

The maxima command is: limit((1+sqrt(n+1))^(-n-1)/(1+sqrt(n))^(-n),n,inf)

Returns zero with Maxima 5.24.0 and is not evaluated when running in http://sagecell.sagemath.org/

robert.marik gravatar imagerobert.marik ( 2015-02-01 16:36:56 -0600 )edit

Thanks @robert.marik - I reported this upstream at https://sourceforge.net/p/maxima/bugs...

kcrisman gravatar imagekcrisman ( 2015-02-03 08:22:36 -0600 )edit

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Asked: 2015-01-30 04:20:28 -0600

Seen: 161 times

Last updated: Jan 30 '15