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 <[email protected]> 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 <[email protected]> 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 [email protected]. >> To post to this group, send email to [email protected]. >> 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 [email protected]. To post to this group, send email to [email protected]. 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.
