issue on infinite series

[sinan...@gmail.com]

Hi,

I would like to report the following:

I tried to integrate 1/x^2 from -oo to oo, and here is what I got:

--

In cocalc, the series is calculated wrongly:

'SageMath version 10.4, Release Date: 2024-07-19'

in: integral(1/x^2, (x,-oo,oo))

out: 0

--

In sagecell.sagemath.org, everything seems to be fine:

'SageMath version 10.2, Release Date: 2023-12-03'

integral(1/x^2, (x,-oo,oo))

ValueError: Integral is divergent.

Thanks,

[Vincent Delecroix]

Hi,

What did you expect? The function 1/x^2 is not integrable at 0. The
following (convergent) integrals does work

sage: integral(1/x^2, (x, 1, +oo))
1
sage: integral(1/x^2, (x, -oo, -1))
1

The following (divergent) integral produces the same result

sage: integral(1/x^2, (x, -1, 1))
Traceback (most recent call last):
...
ValueError: Integral is divergent.

Note that this kind of questions is better directed to either
https://ask.sagemath.org or https://groups.google.com/g/sage-support.

Best
Vincent

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[Nils Bruin]

On Thursday 10 October 2024 at 09:02:58 UTC-7 sinan...@gmail.com wrote:

Hi,

I would like to report the following:

I tried to integrate 1/x^2 from -oo to oo, and here is what I got:

--

In cocalc, the series is calculated wrongly:

'SageMath version 10.4, Release Date: 2024-07-19'

in: integral(1/x^2, (x,-oo,oo))

out: 0

--

 

I've not been able to reproduce this behaviour or SageMath 10.5.beta6. I get the expected "Integral is divergent" error there. You may be observing a regression whatever maxima version cocalc is using for its SageMath 10.4 (most likely whatever sagemath ships with) that is either not present on other systems or has been resolved by a maxima version upgrade in 10.5.beta.

[Dima Pasechnik]

Hi,
how do you run cocalc? At least, on cocalc.com with Sage 10.4, it works OK.

Best,
Dima

[Sinan Kapçak]

Hi, 

You might have missed the first part of my message. I know that the integral is divergent but Sage says it is zero. Thanks.

Best,

Sinan

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[Sinan Kapçak]

Here below, the first line Out [57] says zero. Now, I have just tried again, Out [1] at the bottom, and it gave the correct result. Something strange happened.

 

Sorry if this is posted in the wrong group. Next time, I'll make sure to post in the groups Vincent mentioned.

Thanks,

Sinan

[Dima Pasechnik]

It could be that in one of the 1st 56 commands you broke "integral". Python allows you to redefine things.

e.g.

def intergral(a,b):

      return 0

is one way to achieve this.

HTH

Dima

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[Sinan Kapçak]

I don't think that was the case. I didn't define anything. Also, as shown in the image, Out[55] and Out[61] are functioning correctly for the integral command. 

After reloading the page on another PC, everything, strangely, worked fine.

Best,

Sinan

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