So the problem, is that I want to walk A to B under the fastest time. If I had no constraints, then the answer is simple, simply a straight line from A to B but here I have some constraint which makes it complicated.
Here are my rules and set up: I can make along the purple path from A to B, but I can also move in the region enclosed by ABC in the following ways:
- I can move a 'step' to the right (however steps crossing BC is not allowed)
- Similarly I can step directly in the direction of B
- I can take a step 'up' so I get closed to AB (though I can never cross it)
You may take step size as large or small as you want.
I want to rigorously prove that for any sequence of the three steps I have described above which terminates with ending at B from starting at A, the amount of distance I travel will be less than if I walked by going along AD then to DB
