Status: New
Owner: ----
Labels: Type-Defect Priority-Medium
New issue 2455 by [email protected]: limit evaluation error
[limit(1/cos(x), x, pi/2, dir='+') = ∞]
http://code.google.com/p/sympy/issues/detail?id=2455
VERSION 0.6.7-git
This may be related to the open defect 776
http://code.google.com/p/sympy/issues/detail?id=776
The limit of sec(x) as x approaches pi/2 should be infinity from the left
and negative infinity from the right (limit(1/cos(x), x, pi/2, dir='+')).
The limit from the left erroneously evaluates to positive infinity. The
limit(1/cos(x), x, pi/2) should fail to exist because the limit from the
left and the right approach different values. The graph of the function did
not show any odd behavior.
In [64]: limit(1/cos(x), x, pi/2, dir='-')
Out[64]: ∞
In [65]: limit(1/cos(x), x, pi/2, dir='+')
Out[65]: ∞
In [66]: limit(cos(x), x, pi/2, dir='+')
Out[66]: 0
In [67]: limit(cos(x), x, pi/2, dir='-')
Out[67]: 0
In [68]: limit(-cos(x), x, pi/2, dir='-')
Out[68]: 0
In [69]: limit(-cos(x), x, pi/2, dir='+')
Out[69]: 0
In [70]: limit(-1/cos(x), x, pi/2, dir='-')
Out[70]: -∞
In [71]: limit(-1/cos(x), x, pi/2, dir='+')
Out[71]: -∞
In [72]: limit(-1/cos(x), x, pi/2)
Out[72]: -∞
In [73]: limit(1/cos(x), x, pi/2)
Out[73]: ∞
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