How to show that partial derivative of action is Energy. action of system $S[q_1,q_2, t_1, t_2]$ is integral by time of system Lagrangian. I need to show that partial derivatives by $t_1$ and $t_2$ is Energy.
$$\frac{\partial S }{\partial t_1} = - \frac{\partial S }{\partial t_2} = E$$
