An old puzzle that has been around for a long time
in
various forms is the following. Suppose that a person
on the surface
of the earth walks 1 mile south, then 1 mile
east, then 1 mile north and is back
where they started from.
Where was the starting point? There is one standard
answer to
this puzzle usually given. Less often mentioned
is the fact that there are an infinite number of starting
points possible. Find the exact location of them all.
For the purposes of your solution you may assume that
the
earth is a perfect sphere with a radius of 4000 miles.