#13271: wrong sign with function Ei and limit
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Reporter: dkrenn | Owner: burcin
Type: defect | Status: needs_review
Priority: major | Milestone: sage-5.3
Component: symbolics | Resolution:
Keywords: Ei limit sign | Work issues:
Report Upstream: N/A | Reviewers: Benjamin Jones
Authors: Karl-Dieter Crisman | Merged in:
Dependencies: #11143 | Stopgaps:
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Description changed by benjaminfjones:
Old description:
> We have
> {{{
> sage: (Ei(-Z)).limit(Z=oo)
> Infinity
> }}}
> which is wrong, since it should be 0. It seems that there goes something
> wrong with the {{{-}}} sign. This can be also seen here:
> {{{
> sage: (Ei(-Z)).limit(Z=1000)
> -Ei(1000)
> sage: (Ei(-Z)).limit(Z=1000).n()
> -1.97204513714124e431
> }}}
> But
> {{{
> sage: Ei(-1000).n()
> -5.07089306023517e-438
> sage: -Ei(1000).n()
> -1.97204513714124e431
> }}}
> which are the correct results.
New description:
We have
{{{
sage: (Ei(-Z)).limit(Z=oo)
Infinity
}}}
which is wrong, since it should be 0. It seems that there goes something
wrong with the {{{-}}} sign. This can be also seen here:
{{{
sage: (Ei(-Z)).limit(Z=1000)
-Ei(1000)
sage: (Ei(-Z)).limit(Z=1000).n()
-1.97204513714124e431
}}}
But
{{{
sage: Ei(-1000).n()
-5.07089306023517e-438
sage: -Ei(1000).n()
-1.97204513714124e431
}}}
which are the correct results.
----
Apply [attachment:trac_13271-Ei-maxima.2.patch] to Sage library.
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13271#comment:9>
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