begin
theorem Th1:
theorem
theorem
theorem
theorem Th5:
theorem Th6:
begin
reconsider z = 0 as Element of {0} by TARSKI:def 1;
theorem Th7:
theorem Th8:
theorem Th9:
theorem Th10:
theorem Th11:
theorem Th12:
theorem Th13:
theorem Th14:
theorem Th15:
theorem Th16:
theorem Th17:
theorem Th18:
theorem Th19:
theorem Th20:
theorem Th21:
theorem
theorem Th23:
theorem Th24:
theorem
theorem Th26:
theorem
begin
theorem Th28:
theorem Th29:
theorem Th30:
theorem Th31:
theorem