#7165: an other bug in plot, real_part, imaginary_part and sqrt.
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Reporter: fmaltey | Owner: was
Type: defect | Status: new
Priority: major | Milestone: sage-4.1.2
Component: graphics | Keywords:
Work_issues: | Author:
Reviewer: | Merged:
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I use sage 4.1.2alpha4. This plot is right with this version :
{{{parametric_plot([real(exp(i*m)),imaginary(exp(i*m))],m,0,7)}}}
I apply the patch 7122 by copy/paste in emacs and run sage -br.
Now this plot is also right, it draw a half-circle :
{{{parametric_plot([real(m+sqrt(m^2-1)),imaginary(m+sqrt(m^2-1))],m,-5,5)}}}
I also get it by this function :
{{{
def solve2pplot (eq) : return [real(eq.rhs()),imaginary(eq.rhs())]
res = solve(z^2+2*m*z+1,z)
parametric_plot (solve2pplot (res[0]), m, -5,5)
}}}
Now I solve this 4 degree equation. The solve is right with sqrt at 2
levels.
But I get an error in the parametric_plot :
{{{
res = solve(z^4+2*m*z^2+1,z)
parametric_plot (solve2pplot (res[0]), m, -5,5)
}}}
The local {{{solve2pplot(res[0])}}} generates a long formula.
real axe and imaginary axe are right.
But sage doesn't plot the quarter-circle between axes at position 1=(1,0)
and i=(0,1) and claims {{{failed to evaluate function at 40 points}}}. So
the plot is a line between the 2 axes.
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/7165>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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