Lecture 25, 18.300, Thu May 5, 2022.
Topic: Continue with General first order scalar pde.
% --------------------------------------------------------------------------
1- Short introduction to Variational Calculus. The Euler-Lagrange equations.
2- Fermat's principle.
3- Variational formulation of classical mechanics. Lagrangian and
   Hamiltonian.
4- Interpretation of the phase of the QM wave function, in the
      semi-classical limit, as the action.
   Bi-characteristics/rays satisfy Hamiltonian formulation of classical
      mechanics.
   Propagation of probability along ray tubes.
%
% ==========================================================================
NOTE: Here #nnn	are references to the Lecture Points file.
      [PSQ] means Problem Set Question.
 The "lecture summaries and points" are NOT intended as study materials.
 The points purpose is explained in the "lecture points" file.
 The summaries are brief descriptions each lecture, used by the instructor
 to keep track of the material covered. They ARE *NOT* "lecture notes" to
 be used to study and/or replace attending the lectures, etc. They are
 provided for your convenience, as a help to organize your own notes.
% ==========================================================================
% EOF