Tim Lahey wrote:
> \frac{d}{d t}\left(\frac{\partial L}{\partial \dot{q_i}}\right)
> = \left(\frac{\partial L}{\partial q_i}\right)
>
> where i=1,...,n and L(q_i,\dot{q_i},t). Note that q_i
> is a function of at least t. This is the Euler-Lagrange
> equation. It's the basis for most advanced dynamics.
>
> So, I want to differentiate L with respect to \dot{q_i) and
> q_i as if they were just x and t in a normal derivative.
> This is why my code replaces the functions with symbols and
> then takes the derivative with respect to these placeholder
> symbols and then reverses it.
FWIW Maxima likes to see dy/dx in formulations of
differential equations instead of dy(x)/dx so I think maybe
this problem of whether y is a variable or a function doesn't
really come into play; Maxima can always handle y as a
variable. You could ask on the Maxima mailing list to see
if anyone has worked with Lagrangian mechanics in Maxima.
Robert Dodier
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