theorem Th42:
  [q,t,K,f] in SepQuadruples p & x.u in f.:still_not-bound_in q implies u<t
proof
  assume that
A1: [q,t,K,f] in SepQuadruples p and
A2: x.u in f.:still_not-bound_in q;
  f.:still_not-bound_in q c= f.: (still_not-bound_in p \/ K) by A1,Th38,
RELAT_1:123;
  then x.u in f.:(still_not-bound_in p \/ K) by A2;
  then x.u in f.:still_not-bound_in p \/ f.:K by RELAT_1:120;
  then x.u in f.:still_not-bound_in p or x.u in f.:K by XBOOLE_0:def 3;
  hence thesis by A1,Th39,Th41;
end;
