theorem
  SetPrimenumber m c= Seg m
proof
  let x be object;
  assume
A1: x in SetPrimenumber m;
  then reconsider x as Element of NAT;
  x is prime by A1,Def7;
  then
A2: 1 <= x by INT_2:def 4;
  x < m by A1,Def7;
  hence thesis by A2;
end;
