Nalezn�te maximum a minimum funkce $f$ na mno�in� $K.$
$f(x,y) = \frac 14 [1 + \cos (2x + 2y) + \cos 2x + \cos 2y],
K = \{[x,y] \in \Bbb R^2; \, x \in [0, \pi], y \in [0,\pi]\}.$
