Keep in mind that indefinite integrals are only defined up to a constant. simplify(u.diff(x) - c(x)*c(x-y)) gives 0, which demonstrates that the integral is correct.
As to why they are different, for some reason, integrate isn't giving arctangents in the former case. This could be considered a bug (integrate() should avoid introducing complex numbers whenever possible). Aaron Meurer On Thu, Nov 10, 2016 at 6:22 PM, qm <[email protected]> wrote: > Why do these identical elementary integrations lead to differing results? > In the 1st version the parameters y,G are kept arbitrary before doing the > integration. > In the 2nd version the parameters are set before the integration. > The integrand is completely harmless, both with respect to the variable and > the parameters. > The results differ. Why? > > x,y,G=sp.symbols('x y G') > > c = lambda x: G/(x**2+G**2) > > u=sp.integrate(c(x)*c(x-y),x) > > d = (c(x)*c(x-y)).subs({y:sp.Integer(2),G:sp.Integer(1)}) > > v=sp.integrate(d,x) > > > print (u.subs({x:sp.Integer(1),y:sp.Integer(2),G:sp.Integer(1)})).evalf() > > print (v.subs({x:sp.Integer(1)})).evalf() > > > -0.392699081698724 + 0.e-21*I > > 0 > > > > -- > 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/ef11d5e4-a7c2-434c-b9c9-8236bec34468%40googlegroups.com. > 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%3D6JLGewKhExxwg8xf6nTqvLJJMHmmBVAdAsGyekHx%3DvfAw%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
