#11934: Symbolic simplification error
------------------------------------+---------------------------------------
Reporter: mjo | Owner: burcin
Type: defect | Status: needs_info
Priority: major | Milestone: sage-5.10
Component: symbolics | Resolution:
Keywords: | Work issues:
Report Upstream: N/A | Reviewers:
Authors: Michael Orlitzky | Merged in:
Dependencies: #12322 | Stopgaps:
------------------------------------+---------------------------------------
Changes (by kcrisman):
* status: needs_review => needs_info
Comment:
I'm questioning whether this really is fixing anything. First, it's
still there with `simplify_radical`.
{{{
sage: f = sqrt(-8*(4*sqrt(2) - 7)*x^4 + 16*(3*sqrt(2) - 5)*x^3)
sage: f.subs(x=-1/2).n()
1.47861134210963
sage: f.simplify_radical().subs(x=-1/2).n()
1.47861134210963 - 9.05388323648765e-17*I
}}}
Secondly, the problem is really this. Notice I'm not simplifying anything
at all here.
{{{
sage: h = I*x^(1/2)
sage: h(x=-1/2)
I*sqrt(-1/2)
sage: h(x=-1/2).n()
-0.707106781186548 + 4.32978028117747e-17*I
}}}
Needs work/info, but not because of your patch or #12737, but rather
because this doesn't really treat the underlying issue. This could just
be some floating point thing that is inherently impossible to avoid once
one allows complex numbers (and since your original example is complex
sometimes, the answers are going to be complex, unfortunately).
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11934#comment:6>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
--
You received this message because you are subscribed to the Google Groups
"sage-trac" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at http://groups.google.com/group/sage-trac?hl=en.
For more options, visit https://groups.google.com/groups/opt_out.
