Re: General--Different Results
- To: mathgroup at smc.vnet.net
- Subject: [mg69447] Re: General--Different Results
- From: p-valko at tamu.edu
- Date: Wed, 13 Sep 2006 04:01:00 -0400 (EDT)
- References: <ee64m2$7jl$1@smc.vnet.net>
If you put
Assumptions -> {a > 0, κ > 0, ν > 0}
into the Integrate, you will get always the same answer.
Regards
Peter
aerolapo at hotmail.com wrote:
> I'va got problem in solving this equation,
>
> -((4*Pi*Subscript[ϵ, 0]*n^2*Subscript[k, 0]*A^2)*Abs[ν]*
>
> Integrate[r^2*BesselJ[ν, κ*r]*BesselJ[ν - 1, κ*r],
> {r, 0, a}])/((κ*c)*ν)
>
> because sometimes (the first two or three times I calculate it after opening Mathematica) the result is:
>
> -((4^(1 - ν)*a^3*A^2*n^2*Pi*(a*κ)^(2*ν - 1)*abs[ν]*
>
> HypergeometricPFQ[{ν + 1/2}, {2*ν, ν + 2}, (-a^2)*κ^2]*
> Subscript[k, 0]*Subscript[ϵ, 0])/(c*κ*ν*Gamma[ν]*
> Gamma[ν + 2]))
>
> and some other times: (after two or three identical calculation the result change and it is always this one)
>
> -((2*a^2*A^2*n^2*Pi*Abs[ν]*(ν*BesselJ[ν, a*κ]^2 -
>
> (ν - 1)*BesselJ[ν - 1, a*κ]*BesselJ[ν + 1, a*κ])*
> Subscript[k, 0]*Subscript[ϵ, 0])/(c*κ^2*ν))
>
> Note that I run exaclty the same procedure in both cases (only the expression on the notebook, I press shift+enter, but if I cancel the result and retype shift+enter it sometimes changes).
>
> I don't know if the two of them are equivalent, but, is it possible there is a mistake and only one of them is correct? Is there a method to test the equivalence? If they are equivalent, which is the rule followed by Mathematica to choose the result to return?
>
> Thank you very much.
>
> Jacopo
>
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