title: Points
author: tiglari

For more sophisticated applications, we need to get straight
on the difference between 'points' and 'vectors'.  Although
vectors are widely used to represent points, there is an
important difference between them: vectors can be added to
each other, and multiplied by numbers, but these operations
make no sense for mere points.  What they do make sense for
is <strong>relationships</strong> between points.  If we have
points <b>a</b> and <b>b</b>, it make sense to look for a
point <b>c</b> that is in the same direction from <b>a</b>
as <b>b</b> is, but twice as far away.
