The last entry                a7
--------------------------------

   F1 =. > 0 0 5 ; 8 0 2 ; 9 9 3 ; 1 4 1        NB. The photo coordinates.

   vec =.  , @ ( 3& }. )        NB. Vector in the last row
   vec F1
1 4 1

   normalize =. % _1&{@(#~ -.@(0&=))"1

   normalize F1
0 0 1
4 0 1
3 3 1
1 4 1

   norm =. ". @ ( 20.9&":) @ normalize

   pr =. +/ .*                     NB. Matrix (or dot) product.


