Derivation of the Lagrangian.
117990
Derivation of the method of Lagrange multipliers?
111611
When can we add a total time derivative of $f(q, \dot{q}, t)$ to a Lagrangian?
158576
Derivation of the quadratic equation
70880
Invariance of canonical Hamiltonian equation when adding the total time derivative of a function of $q_i$ and $t$ to the Lagrangian
77253
Proof of Lagrange Identity
83917
How can I prove that the following Lagrangian is Lorentz-invariant iff the axionic field is a pseudoscalar?
44239
Why the extra term $\frac{1}{2}(\partial_{\rho}A^{\rho})^2$ in the photon Lagrangian?
91314
Advantages of Lagrangian Mechanics over Newtonian Mechanics
13644
Is the change in the Lagrangian always a total derivative for symmetry transformations of the action?
104171
Geometric derivation of wave equation
10953
Elementary argument for conservation laws from symmetries *without* using the Lagrangian formalism
112209
Landau's argument for dependence of Lagrangian on magnitude of velocity
135071
Energy momentum tensor from Noether's theorem
153656
What Lagrangian counterterms might be needed in a $\phi^ 6$ theory in 3D?
73045
Transitioning between Lagrangian and Eulerian fluid variables
17451
Expanding electromagnetic field Lagrangian in terms of gauge field
51122
Lagrangian of Schrodinger field