theorem Th3:
  z|^13 = z*z*z*z*z*z*z*z*z*z*z*z*z
  proof
A1: 13 = 12+1;
    z|^12 = z*z*z*z*z*z*z*z*z*z*z*z by Th2;
    hence thesis by A1,NEWTON:6;
  end;
