Did you try using limit()? subs() just inserts the value into the expression, which means that it won't always compute things at infinity correctly.
SymPy's limit() implements a powerful algorithm due to Gruntz, which can take some pretty complicated limits (it is much more powerful than l'Hopital's rule). Aaron Meurer On Sat, Jun 15, 2013 at 10:26 PM, Shriramana Sharma <[email protected]> wrote: > Hello. > > I working on some bezier-related algorithms and need to be able to > provide the curvature of a bezier at any queried point. Now when cubic > beziers have cusps, their curvature is infinite. However the infinity > can be positive or negative. The question is how to find out the sign > of this infinity. > > Now it is a fundamental property of cusps that the sign of curvature > on either side of the cusp is the same, so it stands to reason that if > the curvature sign on the sides is positive then the curvature at the > cusp is positive infinity and likewise for negative. So one method to > find the sign of the infinity is to evaluate the sign at a nearby > point. However I'd like to do it analytically. > > As the attached SymPy script demonstrates, it is possible to evaluate > the limit of the curvature and determine whether the infinity is > positive or negative. However, L'Hopital's rule seems to fail. What is > the method by which SymPy arrives at this result? > > Thank you! > > -- > Shriramana Sharma ஶ்ரீரமணஶர்மா श्रीरमणशर्मा > > -- > You received this message because you are subscribed to the Google Groups > "sympy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/sympy. > For more options, visit https://groups.google.com/groups/opt_out. > > -- You received this message because you are subscribed to the Google Groups "sympy" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/sympy. For more options, visit https://groups.google.com/groups/opt_out.
