This worksheet uses Fermat's Principle of the fastest path in order to discover the Law of Reflection. One has to find the fastest path between two points by moving the point of incidence along the reflecting surface. One can arbitrarily choose the positions of the starting and end points.
Rather simple and intuitive, but still good to discover directly.
This worksheet also is a good introduction to the "sequel" "The Law of Refraction with Fermat's Principle".
