theorem Th98:
  for X, D be non empty set, p be Function of X,D, i be Element
  of X holds p/.i = p.i
proof
  let X, D be non empty set, p be Function of X,D, i be Element of X;
  i in X;
  then i in dom p by Def1;
  hence thesis by PARTFUN1:def 6;
end;
