Comment #4 on issue 1172 by Vinzent.Steinberg: example: curve sketching
http://code.google.com/p/sympy/issues/detail?id=1172
Sympy regressed and fails to find some simple roots:
graph discussion for f(x) = -9*x + x**3
f is symmetric to point of origin.
limes for x -> oo: oo
limes for x -> -oo: -oo
intersections with x-axis:
(3, 0)
(0, 0)
(-3, 0)
intersection with y-axis:
(0, 0)
minimum at (3**(1/2), -6*3**(1/2))
maximum at (-3**(1/2), 6*3**(1/2))
inflection point at (0, 0)
graph discussion for f(x) = 4*x*(1 - a*x**(1/2))
<type 'exceptions.AssertionError'> # regression
graph discussion for f(x) = x**x
limes for x -> oo: oo
limes for x -> -oo: oo # wrong
<type 'exceptions.NotImplementedError'> Unable to solve the equation. #
this is ok
graph discussion for f(x) = log(a**(-3) - x**2)/a
f is symmetric to y-axis.
limes for x -> oo: oo
limes for x -> -oo: oo
<type 'exceptions.NotImplementedError'> Unable to solve the equation.
Sympy should be able to solve such simple equations involving log, for
instance
solve(log(e), x) <=> solve(Eq(e, 1), x)
Attachments:
graph.py 2.6 KB
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