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Re: Integration Problem

  • To: mathgroup at
  • Subject: [mg126369] Re: Integration Problem
  • From: Bill Rowe <readnews at>
  • Date: Fri, 4 May 2012 06:25:55 -0400 (EDT)
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On 5/3/12 at 4:34 AM, michael.musheghian at (Michael
Musheghian) wrote:

>I found that evaluation of this 2 integrals yield a bit different
>result. What could be the reason?

>Integrate[E^(-1/10 ((1 + r2z)^2)), {r2z, -Infinity, Infinity}]

>Integrate[E^(-0.1 ((1 + r2z)^2)), {r2z, -Infinity, Infinity}]

The first gives an exact result, the second a numerical approximation. The 
small complex component of

In[2]:= Integrate[E^(-0.1 ((1 + r2z)^2)), {r2z, -Infinity, Infinity}]

Out[2]= 5.60499 -2.03152*10^-16 I

is the result of small errors introduced by imprecise values. Do

In[3]:= Chop@
 Integrate[E^(-0.1 ((1 + r2z)^2)), {r2z, -Infinity, Infinity}]

Out[3]= 5.60499

to get rid of it.

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