theorem Th6:
  the_antecedent_of (p => q) = p & the_consequent_of (p => q) = q
proof
  p => q is conditional;
  then
  p => q = (the_antecedent_of (p => q)) => (the_consequent_of (p => q)) by
ZF_LANG:47;
  hence thesis by ZF_LANG:32;
end;
