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MathGroup Archive 2007

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Infinity appears as a factor in Integrate result! 2

  • To: mathgroup at smc.vnet.net
  • Subject: [mg74863] Infinity appears as a factor in Integrate result! 2
  • From: "dimitris" <dimmechan at yahoo.com>
  • Date: Mon, 9 Apr 2007 06:10:13 -0400 (EDT)

I forgot to mention that the definite integral for specific a,b is
correct.

In[11]:=
Integrate[1/(x^3 + 1*x^2 + 2*x + 1), {x, 0, Infinity}]

Out[11]=
(1/23)*(Log[Root[-1 + 2*#1 - #1^2 + #1^3 & , 2]^Root[529 - 115*#1 +
#1^3 & , 3]*(-Root[1 + 2*#1 + #1^2 + #1^3 & , 2])^
      Root[529 - 115*#1 + #1^3 & , 2]] + Log[Root[-1 + 2*#1 - #1^2 +
#1^3 & , 1]]*Root[529 - 115*#1 + #1^3 & , 1])

In[12]:=
{N[%], NIntegrate[1/(x^3 + 1*x^2 + 2*x + 1), {x, 0, Infinity}]}

Out[12]=
{0.6681237447686404 + 0.*I, 0.6681237447686608}

Dimitris



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