\[\left\{ \begin{matrix} x^{2} + y^{2} \leq 16 \\ y \geq |x|\text{\ \ \ \ \ \ \ \ \ \ \ \ } \\ \end{matrix} \right.\ \]
\[Сектор\ круга\ радиусом\ 4.\]
\[S = \frac{4^{2}\pi}{4} = 4\pi.\]