I wanted to make a plot of x^3+y^3=1729 (the well-known taxicab problem).
I'm sure there are better ways of acieving this but I opted for a naive
approach:
{{{
def sng(x):
if x < 0:
return -1
return 1
def f(x):
y3 = 1729 - x^3
return sgn(y3) * abs(y3)^(1/3)
}}}
{{{
c = parametric_plot((x,f(x)),-15,15)
c.show()
}}}
(I want to add other things to the plot).
However, when I run this in the notebook, the plot has a cusp at x=12+
and behaves as if the sgn(x) has been taken as +1. I tried evaluating
f(x) at 12 and 13 and the result changes sign as I'd expect.
Am I doing something totally stupid or is there a bug here?
Bill
(still running 2.10.1.rc3 on Linux, Ubuntu 7.10 on a Toshiba Equium laptop)
--
+---------------------------------------+
| Bill Purvis, Amateur Mathematician |
| email: [EMAIL PROTECTED] |
| http://bil.members.beeb.net |
+---------------------------------------+
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