Решебник по алгебре и начала математического анализа 11 класс Колягин Задание 31

\[y = \cos x.\]

\[1)\ \left( \frac{\pi}{2};\ 0 \right):\]

\[y\left( \frac{\pi}{2} \right) = \cos\frac{\pi}{2} = 0;\]

\[2)\ \left( \frac{10\pi}{3};\ \frac{1}{2} \right):\]

\[y\left( \frac{10\pi}{3} \right) = \cos\frac{10\pi}{3} = \cos\frac{4\pi}{3} = - \frac{1}{2};\]

\[3)\ \left( \frac{25\pi}{6};\ - \frac{\sqrt{3}}{2} \right):\]

\[y\left( \frac{25\pi}{6} \right) = \cos\frac{25\pi}{6} = \cos\frac{\pi}{6} = \frac{\sqrt{3}}{2};\]

\[4)\ \left( - \frac{19\pi}{4};\ - \frac{\sqrt{2}}{2} \right):\]

\[y\left( - \frac{19\pi}{4} \right) = \cos\left( - \frac{19\pi}{4} \right) =\]

\[= \cos\frac{3\pi}{4} = - \frac{\sqrt{2}}{2}.\]