Two Trees
I am wandering on the grasslands and I notice two tall trees in the distance that appear to me to be exactly the same height. Now I know those trees. I call them A and B, and it is known that B is exactly twice as tall as A. To amuse myself I decide to try to walk towards the trees in such a way that they always appear to me to be the same height. What can you say about the shape of the path I will have to follow?
Well since B is twice the height of A, every point on my path will need to be twice as far from B as from A.
