Re: Different results with FourierTransform[]

*To*: mathgroup at smc.vnet.net*Subject*: [mg97633] Re: Different results with FourierTransform[]*From*: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>*Date*: Tue, 17 Mar 2009 05:01:34 -0500 (EST)*Organization*: Uni Leipzig*References*: <gpl5sh$ou6$1@smc.vnet.net>*Reply-to*: kuska at informatik.uni-leipzig.de

Hi, and more surprising I have a third one, and this is the correct one Integrate[Tanh[x]*Exp[I*x*p], {x, -Infinity, Infinity}] gives Integrate::idiv:Integral of E^(I*p*x) Tanh[x] does not converge on {-Infinity,Infinity} Regards Jens Wieland Brendel wrote: > Dear reader, > I somewhat stumbled over the following behaviour of mathematica: I tried > to calculate the fouriertransform of Tanh[x]. I did this in two ways: > > 1. Directly: > InverseFourierTransform[Tanh[x], x, p] > > 2. Indirectly: > InverseFourierTransform[Tanh[B x], x, p] > > where I set B -> 1 in the end. > > However, the result between the two approaches differs: Whereas in the > first approach I get a complex number (with both real and imaginary part > being non-zero for almost all values of p), the result in the second > approach yields NO real part; the imaginary part however is the same as > in the first approach. Is there any explanation for this behaviour? > > Thanks a lot in advance! I am really stuck with that... > Wieland > >