[Maxima-bugs] [ maxima-Bugs-991628 ] integrate(x^n,x,a,b) wrong for a<0<b

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Bugs item #991628, was opened at 2004-07-15 08:45
Message generated for change (Settings changed) made by robert_dodier
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>Category: Lisp Core - Integration
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Stavros Macrakis (macrakis)
Assigned to: Nobody/Anonymous (nobody)
Summary: integrate(x^n,x,a,b) wrong for a<0<b

Initial Comment:
integrate(x^n,x,a,b);
Is  n  positive, negative, or zero? neg;
Is  n + 1  zero or nonzero? n;
Is  b - a  positive, negative, or zero? pos;
  => b^(n+1)/(n+1)-a^(n+1)/(n+1)  (NO!)

This is incorrect for (e.g.) n=-2, a<0<b:

integrate(x^-2,x,a,1);
Is  a - 1  positive, negative, or zero?  neg;
  => Integral is divergent (OK)

Same thing, but a more dramatic demo:

  assume(equal(a,-1),equal(b,1),equal(n,-2));
  integrate(x^n,x,a,b) =>
     b^(n+1)/(n+1)-a^(n+1)/(n+1)  (NO!)

vs.

  integrate(x^-2,x,-1,1) => Divergent (OK)

Also

  assume(equal(n,-2));
  integrate(x^n,x,-1,1); => (-1)^n/(n+1)+1/(n+1)  (NO!)



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