Distance
=========

Write a function *dist3(x1,y1,x2,y2)*
that takes the cartesian coordinates of two points on
the plane
*(x1,y1)* i *(x2,y2)*
and returns the distance in norm 3 between the two points.
This distance is defined as:
:math:`\sqrt[3] { \left| x1-x2 \right| ^3 + \left|y1-y2
\right| ^3 }`