Status: New
Owner: ----
Labels: Type-Defect Priority-Medium
New issue 3330 by [email protected]: Taylor expansion wrong for this
expression?
http://code.google.com/p/sympy/issues/detail?id=3330
The documentation on the series expansion is a little sparse so I hope I
understand it correctly.
For a given function f(x) I expect that f.series(x, x0=0) or alternatively
f.taylor_term(n, x) returns a Taylor expansion of the function.
My test case looks as follows:
from sympy import *
c, x = symbols('c x')
f = (c**2 + x)**(0.5)
Now
f.series(x, x0=0, n=1)
returns
(1 + 0.5*x/c**2 - 0.125*x**2/c**4)*(c**2)**0.5 + O(x)
similarly
f.taylor_term(0,x)
returns
1
The first term in a Taylor expansion should be f(x=x0), so I would expect
that the first term is (c**2)**(0.5), as Wolfram Alpha returns for example.
I am misinterpreting something here or is this a bug?
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