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Re: Mathematica integration Vs Sympy

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  • Subject: [mg130563] Re: Mathematica integration Vs Sympy
  • From: Alex Krasnov <akrasnov at eecs.berkeley.edu>
  • Date: Sun, 21 Apr 2013 05:16:06 -0400 (EDT)
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Mathematica's Integrate implicitly assumes that parameters have generic 
values. The result can be invalid for special values, in this case, a==1. 
It appears that the same is true for SymPy's integrate, as u.subs({a:1}) 
demonstrates.

For other values, the Mathematica and SymPy results appear to differ by 
a constant of integration. Both results are valid. This is a consequence 
of different integration procedures and can occur even for the same 
integral in different forms in Mathematica and presumably SymPy.

Alex


On Sat, 20 Apr 2013, Sergio R wrote:

> Hello all,
>
>   Just for fun a put an integral I was doing via mathematica
> WolframAlpha
> [  http://www.wolframalpha.com/input/?i=Integrate[1%2F%28x*%281-a*%281-x%29%29%29%2Cx]
> ]
> into the online sympy [ http://live.sympy.org/ ] console
> the following:
>
> a = Symbol('a'); g = 1/(x*(1-a*(1-x))) ; u=simplify(integrate(g,x))
>
> Then, to display the result, at the sympy ">>>" prompt, type u
> and hit return.
>
>  To my surprise,  sympy seems to give the right result without any
> assumption, while mathematica's result seems to assume a>1, which is
> not specified. Also for this case (a>1) sympy gives an extra constant
> which is not present in the mathematica result.
>
> Is there a way to make mathematica to output a general result like
> sympy
> in this case?
>
> Sergio
>



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