
theorem Th13:
  for p be Safe Prime ex q be Sophie_Germain Prime st card (Z/Z*(p )) = 2*q
proof
  let p be Safe Prime;
  consider q be Sophie_Germain Prime such that
A1: 2*q+1 = p by Th10;
  p-1 =2*q by A1;
  hence thesis by INT_7:23;
end;
