theorem
  Ex(x,p '&' q) is valid implies Ex(x,p) '&' Ex(x,q) is valid
proof
  assume
A1: Ex(x,p '&' q) is valid;
  Ex(x,p '&' q) => (Ex(x,p) '&' Ex(x,q)) is valid by Th43;
  hence thesis by A1,CQC_THE1:65;
end;
