reserve n for Nat,
  k for Integer;
reserve p for polyhedron,
  k for Integer,
  n for Nat;

theorem Th69:
  1-th-polytope(p,dim(p)) = p
proof
  reconsider egy = 1 as Nat;
  set s = dim(p)-polytope-seq(p);
A1: s = <*p*> by Def7;
  egy <= num-polytopes(p,dim(p)) by Th29;
  then egy-th-polytope(p,dim(p)) = s.egy by Def12
    .= p by A1;
  hence thesis;
end;
