MathGroup Archive 1997

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Incorrect result for improper integral with MMA?


Chris Barker wrote:
> 
> The command:
> 
> Integrate[1/(x*Log[x]^2),{x,3,Infinity}]
> 
> yields the result:

I am not sure I understand the internal workings of Integrate and the
internal difference between Integrate[f,x] and Integrate[f,{x,a,b}], but


fi[a_]=Integrate[1/(x*Log[x]^2),x]/.x->a;
fi[3]-fi[Infinity]

returns a correct result.  Also,
Integrate[1/(x*Log[x]^2),{x,3,a}]
returns a correct result for any finite a greater than three, including
huge values where the integrand is extremely small.

If I had to guess at a reason, it would be that there is no way that
mathematica can know if a function is reasonably behaved on an interval
that goes to infinity, so it defaults to a different behavior when
Infinity is one of the limits.


  • Prev by Date: prograMing: split a list
  • Next by Date: Font Problem with Mathematica v3.0
  • Previous by thread: Re: Incorrect result for improper integral with MMA?
  • Next by thread: Re: Incorrect result for improper integral with MMA?