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Topic: Mathematica integration Vs Sympy
Replies: 7   Last Post: Apr 23, 2013 9:38 PM

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 Alex Krasnov Posts: 15 Registered: 10/3/12
Re: Mathematica integration Vs Sympy
Posted: Apr 21, 2013 5:17 AM

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
>

Date Subject Author
4/21/13 Alex Krasnov
4/21/13 Brentt
4/22/13 Murray Eisenberg
4/22/13 Alex Krasnov
4/23/13 Richard Fateman
4/23/13 Richard Fateman