I haven't been involved in this thread but I thought I should contribute one
thing, which may be obvious and not necessary. If the problem is
singularities you can solve for the infinite points of expr (in
integrate(expr,x)) by solving solve(1/expr = 0, x). Isn't that the best
way, or maybe if that doesn't work use to_poly_solve. %solve(1/expr,x) to
get the points. Another idea is some analysis of the expression. If you
have ratio of two polynomials then just use solve(denom(expr)=0,x).
Rich
-----Original Message-----
From: Raymond Toy
Sent: Saturday, December 22, 2012 10:33 PM
To: maxima at math.utexas.edu
Subject: Re: [Maxima] strange quad_qags behavior?
>>>>> "Edwin" == Edwin Woollett <woollett at charter.net> writes:
Edwin> I am assuming quad_qags will return a noun
Edwin> form when the integrand has an interior singularity. The expected
Edwin> behavior occurs
Edwin> if the upper limit is 1, but not when the upper limit is
0.999999999999
Your assumption isn't quite right. It returns a noun form if the
integrand is evaluated at a bad point. When the upper limit is 1,
quad_qags evaluates the integrand at exactly 0.5. When the upper
limit is not 1, it's evaluated at a slightly different place.
quad_qags is pretty good, but it's no substitute for some analysis.
Ray
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