/*
   This is a /fourth/ test of the HWEB system of documentation.  This
   test focuses on mathematical formatting.  Consider the parametrization
   of a cylinder as "all points at radius $A$ from the three-dimensional
   line $p = (0,B,C) + t(1,D,E)$."   Okay, that's bogus, but let's go on.
   We have
   $
       p_{ideal} = (0,B,C) + (1,D,E)
       p_{actual,i} = (Xi,Yi,Zi)
   $

   So we have differences $(X',Y',Z')$ in $X,Y,Z$ as follows: $
       X'_i := 0
       Y'_i := Yi - (B+DXi)
       Z'_i := Zi - (C+EXi)
   $

   We want to minimize the sum of squared errors $
       \sum_{i} X'_i^2 + Y'_i^2 + Z'_i^2
   $

   (that is, $\sum_{i\in P_n} X'_i^2 + Y'_i^2 + Z'_i^2$ where $P_n$
   is the number of points involved).  So we have
   $
       \sum_{i\in P_n} X'_i^2 + Y'_i^2 + Z'_i^2
   $
   ...and if that doesn't all come out looking good, then you
   had better switch to TeX or something, because our math formatting
   can't get much better!
*/