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MathGroup Archive 2002

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Re: NIntegrate

  • To: mathgroup at
  • Subject: [mg36527] Re: NIntegrate
  • From: "Rob_jack" <rob_jackNSP at>
  • Date: Wed, 11 Sep 2002 03:27:47 -0400 (EDT)
  • References: <alkhi3$ve$>
  • Sender: owner-wri-mathgroup at

"Rob_jack" <rob_jackNSP at> wrote

There is an error in the previous message.

This is the just msg:

In[1]=f[y_,z_]: = (y^4/( (1+(8.44*10^-4)^2 * (1+z)^2 y^2) (Exp[y]+1) )

In[2]=F[z_]: = NIntegrate[f[y,z], {y, 0, Infinity}

Mathematica 4.0 says:


NIntegrate: : inum : Integrand 1.07577/( 1+7.12336*10^-7 (1. + z)^2 ) is not
numerical at  {y}={1.}.

What is it??

Moreover, I have used the following procedure:
If z<<1,

f[y,z]=Sum[(-1)^n*a^n*(1+z)^2n *(y^(2n+4)/(Exp[y]+1),{n, 0, N} ]

here a=(8.44*10^-4)^2


F[z]:=Sum[(-1)^n*a^n*(1+z)^2n *(y^(2n+4)/(Exp[y]+1) * Gamma[2 n+5]*Zeta[2
n+5],{n, 0, N} ]

this series (N<+oo) only approximates the function for small z, and me it
interests the behavior of F for z in the range 800-1300.

Thx in advance.


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