Solution of the Airplane Minimum Time Problem by Huygens' Principle

The relationship between Huygen's principle in geometrical optics and the calculus of variations is examined. It is found that the calculus of variations is a straightforward generalization of the theory of geometrical optics. As a consequence, a new and simplified approach to the calculus of variations is obtained. This approach reduces problems in the calculus of variations to problems in ordinary maxima and minima in the calculus. The approach rests heavily on the early work of C. Huygens, 1690, and John Bernoulli, 1718, and its extension by W. Hamilton and C. Caratheodory. New numerical techniques, suggested by this approach are examined and compared and two of these are applied to the airplane minimum time problem.