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MathGroup Archive 2001

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Re: Strange error message from NIntegrate

  • To: mathgroup at smc.vnet.net
  • Subject: [mg28152] Re: Strange error message from NIntegrate
  • From: "Urijah Kaplan" <uak at sas.upenn.edu>
  • Date: Mon, 2 Apr 2001 02:18:23 -0400 (EDT)
  • Organization: University of Pennsylvania
  • References: <9a6e2c$ep2@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

What are those brackets around 3/2 for?

                                                                --Urijah

"Henrik Holm" <h.holm at spray.no> wrote in message
news:9a6e2c$ep2 at smc.vnet.net...
> I am trying to do the following numerical integration:
>
>   NIntegrate[x^{3/2}*Exp[-x]*BesselI[3/2,x/2], {x,0, Infinity}]
>
> this results in the following error,
>
>   NIntegrate::"inum":
>    Integrand {0.141859424324175} is not numerical at {x} = {1.}.
>
> I think this is very strange, after all, 0.1418... _is_ a
> number.  It might be noted that doing the integration
> symbolically works nicely:
>
>   Integrate[x^{3/2}*Exp[-x]*BesselI[3/2,x/2], {x,0, Infinity}]
>
> which gives the following result:
>
>   16/(9*Sqrt[pi])
>
>
> I guess I am doing something wrong, but I cannot understand
> what.  Can anybody help me?
>
>
>
> Regards,
> Henrik Holm
>




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