reserve x,y,z for set;
reserve f,f1,f2,f3 for FinSequence,
  p,p1,p2,p3 for set,
  i,k for Nat;
reserve D for non empty set,
  p,p1,p2,p3 for Element of D,
  f,f1,f2 for FinSequence of D;

theorem Th42:
  f <> {} implies f/.1 in rng f
proof
  assume f <> {};
  then 1 in dom f by FINSEQ_5:6;
  hence thesis by PARTFUN2:2;
end;
