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Re: Bug in LaplaceTransform?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg97757] Re: Bug in LaplaceTransform?
  • From: dh <dh at metrohm.com>
  • Date: Fri, 20 Mar 2009 02:42:58 -0500 (EST)
  • References: <gpsr23$mf1$1@smc.vnet.net>


Hi Wieland,

sure that's wrong. But why?

Consider:

LaplaceTransform[1, t, a]  ==>  1/a

thats only correct if Re[a]>0, otherwise the transform is not defined. 

Mathematica seems to assumes, that the user only asks reasonable questions. 

Clearly "LaplaceTransform" is less smart than Integrate.

Daniel



Wieland Brendel wrote:

> Dear reader,

> how can it happen that Mathematica throws out -i for the Laplace 

> transform of one,

> 

> LaplaceTransform[1, t, I] = -i?

> 

> After all the Laplace transformation (with s = I) is defined as

> 

> Integrate[Exp[-I t], {t, 0, Infinity}]

> 

> and should be undefined. Am I wrong or is this a bug?

> 

> Thanks for an answer!

> Wieland

> 




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