strange, a friend told me that it works in Mapple. I will ask him some input file, and paste it here.
My goal is to use Lagrange Equation, something like this: http://en.wikipedia.org/wiki/Lagrangian_mechanics#Falling_mass If you check the 3rd equation of that example, you can see what I would like to do. the kinetic energy must be derive regarding x' and then t and x is a function of time. x=f(t) is there a good approch to do that in sympy ? thanks for your help ! On 31 oct, 17:20, Andy Ray Terrel <[email protected]> wrote: > AFAIK, general Fréchet derivatives aren't available in any computer > algebra system. You would have to hand roll something to expand the > chain rule. Generally, the existence of such a derivative isn't > available. For fun I tried your example in Mathematica and even there > you get a recursion limit error. > > -- Andy > > On Sat, Oct 30, 2010 at 7:16 AM, Philippe <[email protected]> wrote: > > Hi, > > > I am new to sympy. > > I try to derive an equation of that form: T = k * x' > > x if a function of time ; x = f(t) > > x' is diff(x, t) > > > I would like to get > > T2 = diff(T, x') > > T3 = diff(T2, t) > > > Is it possible ? > > I checked the documentation, but couldn't find a way to do that. > > > Thanks for helping ! > > Philippe > > > PS: I try to get it with > > T = m * f(t) > > print diff(T, f(t)) > > does not work :/ > > ValueError: Invalid literal: f(t) is not a valid variable > > > -- > > 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.
