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/ > msgid/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%3D6LLvOKkQxq%2BF5hhAdpFXFYUP-KmqqQSJbJYnEfvn_BBSg%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
