  There are known constructions for some regular polygons, usually inscribed in
a circle, but not for all polygons - the Gauss-Wantzel Theorem states precisely
which ones can be constructed.
  The constructions differ greatly from one polygon to the other. There are,
however, general processes for determining the side of the $n$-gon
(approximately, but sometimes with great precision), which we describe in this
paper. We present a joint mathematical analysis of the so-called Bion and
Tempier approximation methods, comparing the errors and trying to explain why
these constructions would work at all.
