> I noticed that "keepfloat: true" does not get always get honoured by
> maxima. A symptom:
>
> sage: integrate(cos(1.17*x),x)
> 0.854700854701*sin(1.17*x)
>
> (works as expected)
>
> sage: S=integrate(cos(1.17*x^2),x)
> sage: S
> -1/156*((5*I + 5)*sqrt(2)*sqrt(13)*erf((3/20*I -
> 3/20)*sqrt(2)*sqrt(13)*x) + (5*I - 5)*sqrt(2)*sqrt(13)*erf((3/20*I +
> 3/20)*sqrt(2)*sqrt(13)*x))*sqrt(pi)
>
> (surprise!)
In pure Maxima:
(%i1) keepfloat:true$
(%i2) integrate(cos(1.17*x),x);
(%o2) .8547008547008548 sin(1.17 x)
(%i3) integrate(cos(1.17*x^2),x);
rat: replaced -1.17 by -117/100 = -1.17
rat: replaced 1.17 by 117/100 = 1.17
(%o3) - (sqrt(%pi) ((5 sqrt(2) sqrt(13) %i - 5 sqrt(2) sqrt(13))
(3 sqrt(2) sqrt(13) %i + 3 sqrt(2) sqrt(13)) x
erf(----------------------------------------------)
20
+ (5 sqrt(2) sqrt(13) %i + 5 sqrt(2) sqrt(13))
(3 sqrt(2) sqrt(13) %i - 3 sqrt(2) sqrt(13)) x
erf(----------------------------------------------)))/156
20
And apparently that's not quite what keepfloat:true does - see
http://www.math.utexas.edu/pipermail/maxima/2008/010043.html,
http://www.math.utexas.edu/pipermail/maxima/2009/016559.html, and
http://sourceforge.net/tracker/index.php?func=detail&aid=1177935&group_id=4933&atid=104933
for some Maxima list discussion on this issue.
It sounds like in solve this is not likely to be changed, but it is
interesting to see it show up elsewhere. Perhaps Robert D. has some
insight - I don't want to file a Maxima bug ticket if it isn't
considered a bug.
- kcrisman
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