Aaron Thanks for the tips.
Where are the "issues" located? I am numerically evaluating x*cos(x)/sin(x) on [-pi/2,pi/2] and the spurious singularity at x= 0 is giving me grief. x/sin(x)=1 at x=0. After looking at my problem it seems that I should have asked if there is and efficient way to embed sin(x)/x or x/sin(x) in a function that is evaluated at 0. I will probably use a 7th order Taylor series unless there another clever option. The series for x/sin(x) has much better convergence than the series for x*cot(x) in my range of interest (+- pi/2). In [41]: (x/sin(x)).series(x, 0, 8) Out[41]: 1 + x**2/6 + 7*x**4/360 + 31*x**6/15120 + O(x**7) On Jun 2, 12:41 pm, "Aaron S. Meurer" <[email protected]> wrote: > On Jun 2, 2010, at 9:12 AM, Scott wrote: > > > What is the best way to evaluate x * cot(x) evaluated for x=0-pi/2 > > with sympy? > > I am not too sure what you mean by 0-pi/2, but you could try limit(): > > In [3]: limit(x*cot(x), x, 0) > Out[3]: 1 > > In [4]: limit(x*cot(x), x, pi/2) > Out[4]: 0 > > > > > Is there a better option than coding the Taylor series approximation? > > You wouldn't need to code the taylor series, it already is implemented: > > In [7]: print (x*cot(x)).series(x) > 1 - x**2/3 - x**4/45 - 2*x**6/945 + O(x**7) > > > > > Also with the sympy that shipped with Ubuntu 10.04 sympy.cot(0) is 0 > > rather than infinity. > > This is a bug that still exists in master. Could you report it in the issues? > > Aaron Meurer > > > > > V/R > > > Scott > > > -- > > You received this message because you are subscribed to the Google Groups > > "sympy" group. > > To post to this group, send email to [email protected]. > > To unsubscribe from this group, send email to > > [email protected]. > > For more options, visit this group > > athttp://groups.google.com/group/sympy?hl=en. > > -- You received this message because you are subscribed to the Google Groups "sympy" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/sympy?hl=en.
