General--Different Results

*To*: mathgroup at smc.vnet.net*Subject*: [mg69437] General--Different Results*From*: aerolapo at hotmail.com*Date*: Tue, 12 Sep 2006 06:53:37 -0400 (EDT)

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 Link to the forum page for this post: http://www.mathematica-users.org/webMathematica/wiki/wiki.jsp?pageName=Special:Forum_ViewTopic&pid=13453#p13453 Posted through http://www.mathematica-users.org [[postId=13453]]