Re: Integrate gives wrong results for a simple polynomial
- To: mathgroup at smc.vnet.net
- Subject: [mg117952] Re: Integrate gives wrong results for a simple polynomial
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Tue, 5 Apr 2011 06:45:02 -0400 (EDT)
Appears to work fine here. What result did you get and with which system and version.
{$Version, $ReleaseNumber}
{"8.0 for Mac OS X x86 (64-bit) (February 23, 2011)", 1}
$Assumptions = p > 0; Integrate[Subscript[x, 1]*(1 + y)^2, {y, -1, 1}]
(8*Subscript[x, 1])/3
$Assumptions = p > 0; Integrate[x*(1 + y)^2, {y, -1, 1}]
(8*x)/3
$Assumptions = True; Integrate[Subscript[x, 1]*(1 + y)^2, {y, -1, 1}]
(8*Subscript[x, 1])/3
Integrate[(1 + y)^2, {y, -1, 1}]
8/3
Bob Hanlon
---- Micket <micketeer at gmail.com> wrote:
=============
I have had the bad luck to discover a strange bug (?) when computing
some integrals with mathematica.
I simplified it as far as i could;
$Assumptions = p > 0; Integrate[Subscript[x, 1]*(1 + y)^2, {y, -1, 1}]
If i change anything else, be it the assumption (yes, it is a
completely unrelated variable), the subscript, the integration limits,
the exponent, the addition, it works out the correct answer.
It also takes a significant time (a few seconds) to compute this
integral.
Does anyone have an explanation for this behavior?