V kter�ch bodech maj� tot�ln� diferenci�l funkce (v�echny
dodefinovan� v po��tku nulou)
$$
f(x,y) = (x^2+y^2)\sin\frac{1}{x^2+y^2}, \qquad
g(x,y) = \frac{x^2 y (|x| + |y|)}{x^4 + y^2}
$$

$$
h(x,y) = \exp {(-\frac{1}{x^2+y^2+xy})}.
$$
