With that being said, either answer is wrong if you want a real function.
For that, you need log(abs(4 - t)). But unfortunately, the abs() answer
isn't valid in the general complex case, which is why SymPy doesn't return
it.

Aaron Meurer

On Mon, Sep 19, 2016 at 11:42 AM, Aaron Meurer <asmeu...@gmail.com> wrote:

> See https://github.com/sympy/sympy/issues/11017. It would be nice if we
> could fix ratint to not flip signs in the logarithm.
>
> Aaron Meurer
>
> On Mon, Sep 19, 2016 at 2:43 AM, Kalevi Suominen <jks...@gmail.com> wrote:
>
>>
>> There are several integrators in SymPy. The latter form is produced by
>> ratint.
>>
>> >>> from sympy.integrals.rationaltools import ratint
>> >>> from sympy.abc import t
>> >>> ratint(1/(4*(-t + 4)), t)
>> -log(t - 4)/4
>>
>> Kalevi Suominen
>>
>>
>> On Monday, September 19, 2016 at 5:06:22 AM UTC+3, Raphael Timbó wrote:
>>>
>>> Since the images with the results are distorted:
>>>
>>> First result:
>>>
>>> -(1/4)*log(4*t - 16)
>>>
>>> Results given by the step-by=step solution on sympy gamma:
>>>
>>> -(1/4)*log(-t + 4)
>>>
>>>
>>>
>>> On Sunday, September 18, 2016 at 3:18:31 PM UTC-3, Raphael Timbó wrote:
>>>>
>>>> Hi,
>>>> I was trying to use:
>>>> integrate(Rational(1,4)*(1/(4-t)))
>>>>
>>>> This was returning:
>>>> −14log(4t−16)
>>>>
>>>> I was not expecting this result... I went to sympy gamma to see the
>>>> steps and I saw that:
>>>>
>>>> Antiderivative forms:
>>>> <http://gamma.sympy.org/input/?i=integrate%28Rational%281%2C4%29*%281%2F%284-t%29%29%29#integral_alternate_fake>
>>>>
>>>>    - integrate(1/(4*(-t + 4)), t)
>>>>    −14log(4t−16)
>>>>
>>>>
>>>> But when you check the steps you have:
>>>>
>>>> The answer is:
>>>>
>>>> −14log(−t+4)+constant
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> I could not understand why the results are different...
>>>> Any explanation?
>>>>
>>>> Thank you!
>>>>
>>>> --
>> You received this message because you are subscribed to the Google Groups
>> "sympy" group.
>> To unsubscribe from this group and stop receiving emails from it, send an
>> email to sympy+unsubscr...@googlegroups.com.
>> To post to this group, send email to sympy@googlegroups.com.
>> Visit this group at https://groups.google.com/group/sympy.
>> To view this discussion on the web visit https://groups.google.com/d/ms
>> gid/sympy/1629e59a-4d35-4927-89fc-0f3a94a3fd86%40googlegroups.com
>> <https://groups.google.com/d/msgid/sympy/1629e59a-4d35-4927-89fc-0f3a94a3fd86%40googlegroups.com?utm_medium=email&utm_source=footer>
>> .
>>
>> For more options, visit https://groups.google.com/d/optout.
>>
>
>

-- 
You received this message because you are subscribed to the Google Groups 
"sympy" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to sympy+unsubscr...@googlegroups.com.
To post to this group, send email to sympy@googlegroups.com.
Visit this group at https://groups.google.com/group/sympy.
To view this discussion on the web visit 
https://groups.google.com/d/msgid/sympy/CAKgW%3D6%2BQD5cpGzahm7wwkgZNaOw%2Bb3gSVrYTULL-j%3D%2BfeLLgQQ%40mail.gmail.com.
For more options, visit https://groups.google.com/d/optout.

Reply via email to