reserve i,j,k,n for Nat;
reserve D for non empty set,
  p for Element of D,
  f,g for FinSequence of D;

theorem Th38:
  p in rng f implies f/.(p..f) = p
proof
  assume p in rng f;
  then p..f in dom f & f.(p..f) = p by FINSEQ_4:19,20;
  hence thesis by PARTFUN1:def 6;
end;
