Re: Re: Different results with FourierTransform[]

*To*: mathgroup at smc.vnet.net*Subject*: [mg97894] Re: [mg97882] Re: Different results with FourierTransform[]*From*: Daniel Lichtblau <danl at wolfram.com>*Date*: Wed, 25 Mar 2009 05:42:03 -0500 (EST)*References*: <gpl5sh$ou6$1@smc.vnet.net> <gpnscg$go5$1@smc.vnet.net> <200903241034.FAA19949@smc.vnet.net>

schochet123 at gmail.com wrote: > [...] > Unfortunately, there appears to be a bug in Mathematica's calculation > of > InverseFourierTransform of Tanh[x], as the original poster pointed > out. The fact that the answer obtained is wrong can be seen from the > fact that the answer is not odd, which contradicts the fact that the > FourierTransform and InverseFourierTransform of odd functions are odd. > > Sorry if some people see this message twice; when I originally posted > it via thunderbird my message showed up in thunderbird on my local > site but not in google groups. > > Steve Moderated group, takes maybe a day for messages to go out. Devendra Kapadia located the bug in a special case handler (applicable when we have integral convergence at infinity, modulo a constant) and fixed it in the development Mathematica. Turns out to be a missplaced minus sign. From his note to me last week: (ExpToTrig[-Exp[$FFC*I*s*t] should be ExpToTrig[Exp[-$FFC*I*s*t]) Was my bug from 4-5 years ago. [Steve should not be surprised; he may recall me taking an occasional snooze in physics 112, where we covered Fourier transforms.] Daniel Lichtblau Wolfram Research

**References**:**Re: Different results with FourierTransform[]***From:*schochet123@gmail.com