I continue to try to plot in the complex plane the 4 solutions of the
equation :
z^4+2*a*z^2+1 = 0 when a is a real.
I want to get a circle and 2 lines...
Guru ckrisman explains that today this plot seems impossible and gives
me a tip with lambda : .... calls in plot.
I can make more parametric_plot with but I can't get this one.
Guru harald proposes the use of list and list_plot... and I
misunderstand an other sage property :
var ("a,z")
res = solve (z^4 + 2*a*z^2 + 1 == 0, z) # is right
res1 = res[0].rhs() # - sqrt (-a+sqrt(a^2-1)), others have + or -...
res2 = - sqrt (-a+sqrt(a^2-1)) # I type the same expression
[res2 for a in sxrange (-5,5,0.8)] # is right
[res1 for a in sxrange (-5,5,0.8)] # makes an error, even if the display
of the inner formula is the same.
# I try this other case :
b=a
[sqrt(a) for a in sxrange(-2,2,0.8)] # is right
[sqrt(b) for a in sxrange(-2,2,0.8)] # repeat the last value.
# It seems that a remains a numerical variable outside the for loop.
How can I get : build the list, then replace with all values ?
I don't want that sage-gurus solve theses exercices.
My firefox browses a lot of excellent help pages about sage, but I don't
find the right one.
Francois
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