Greetings People!

I am modelling a dynamical system using variational formulation. The final step is to plug in, the energy values, in the Euler-Lagrange Equation. The functional has both explicit dependence on time, and implicit dependence (in the form of the generalised coordinate). Since motive of the exercise is to obtain the governing equations for the generalized coordinates, this implicit dependence is unknown. How can Maple be used to derive the differential equations in this situation?

As an example, consider,

Here, ld and l are variables, which are function of time. In order to calculate the term,

How do I proceed? Thanks in advance.