reserve x, y for object, X, X1, X2 for set;

theorem Th5:
  I_Funcs(X) is Subset of I_PFuncs(X)
proof
  I_Funcs(X) c= I_PFuncs(X)
  proof
    let x be object;
    assume x in I_Funcs(X);
    then x is Function of X,INT by Def17;
    hence thesis by Def16;
  end;
  hence thesis;
end;
