Conservation of energy: Consider the Lagrangian which depends on the generalized coordinates q(t) and their time derivatives q'(t), but which does not depend explicitly on time. Use the Beltrami identity to show that the Hamiltonian, H = p*q' - L, is a conserved quantity. To understand the significance of this result, consider the case where the Lagrangian is that of a particle moving in 3 dimensions, so that the generalized coordinates may be taken to be x, y, and z. Show that in this case, H = T + U.