theorem Th70:
  SetPrimenumber p c= Seg p
proof
  let x be object;
  assume
A1: x in SetPrimenumber p;
  then reconsider q = x as Element of NAT;
  q is prime by A1,Def7;
  then
A2: 1 <= q by INT_2:def 4;
  q < p by A1,Def7;
  hence thesis by A2;
end;
