theorem Th32:
  F => G = F1 => G1 implies F = F1 & G = G1
proof
  assume F => G = F1 => G1;
  then
A1: F '&' 'not' G = F1 '&' 'not' G1 by FINSEQ_1:33;
  hence F = F1 by Th30;
  'not' G = 'not' G1 by A1,Th30;
  hence thesis by FINSEQ_1:33;
end;
