Comment #5 on issue 1321 by fabian.seoane: trigonometric functions of
floating-point numbers should return floating-point numbers
http://code.google.com/p/sympy/issues/detail?id=1321
response to #2 and #4:
sympy already does convert 0.1 to 0.1000000000000000, so you'll inevitably
get
rounding errors (you choosed to use float's, use Rational or Real if you
expect exact
behavior).
my complain is that the following is very confusing:
In [1]: import math, sympy
In [2]: math.cos(0.1)
Out[2]: 0.99500416527802571
In [3]: sympy.cos(0.1)
Out[3]: cos(0.100000000000000)
I think math does it right, as I would expect that if my argument's are
float's the
result will be a float. As I said before, you can't expect an exact result
if you
give a float as an argument. Use Rational if you expect that.
comment to #3:
not sure about what precision we should use. How do other libraries do
(python.mat, scipy, etc)?
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