reserve P,Q,X,Y,Z for set, p,x,x9,x1,x2,y,z for object;
reserve D for non empty set;

theorem
  Funcs(X,Y) c= PFuncs(X,Y)
proof
  let x be object;
  assume x in Funcs(X,Y);
  then ex f being Function st x = f & dom f = X & rng f c= Y by Def2;
  hence thesis by PARTFUN1:def 3;
end;
