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MathGroup Archive 2005

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Re: Integrate vs Nintegrate for impulsive functions

  • To: mathgroup at smc.vnet.net
  • Subject: [mg61706] Re: [mg61690] Integrate vs Nintegrate for impulsive functions
  • From: Chris Chiasson <chris.chiasson at gmail.com>
  • Date: Wed, 26 Oct 2005 02:44:45 -0400 (EDT)
  • References: <200510260501.BAA18782@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

My computer gives the same answer as yours for NIntegrate, but it
thought for a long while on Integrate and then spit out:
Complex[-4.4073414839228176`*^145,6.238877585945074`*^146]
Bug??
Version Number: 5.2.0.0
Platform: Windows

On 10/26/05, Pratik Desai <pdesai1 at umbc.edu> wrote:
> Hi Folks
>
>
> I have an expression resulting from a fourier series (for a 1D wave
> equation for a string) (fourier coeffficient) of the form
>
> h[x_]=(-0.24982234345508192 - 0.0429732983215806*I)*
>  Sin[(3.1734427242687215 + 0.3295480781081674*I)*x]*
>  (Cosh[1000.*(-0.4 + x)^2] - Sinh[1000.*(-0.4 + x)^2])
>
> I try to integrate this on the domain x(0,1) to get the fourier
> coefficient. I get some results that I need help explaining
>
>
> Integrate[h[x],{x,0,1}]
>
>  >>0+0 *I
>
> NIntegrate[h[x],{x,0,1}]
>
>  >>-0.0133612 - 0.00285551 \[ImaginaryI]
>
> Is the result from NIntegrate valid
>
> The initial condition is essentially a smoothed delta function at x=0.4
>
> gxx[x_]=E^(-1000.*(-0.4 + x)^2)
>
> Please advise
>
>
> Regards
>
>
> Pratik .
>
> --
> Pratik Desai
> Graduate Student
> UMBC
> Department of Mechanical Engineering
> Phone: 410 455 8134
>
>
>


--
http://chrischiasson.com/contact/chris_chiasson


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