Решебник по алгебре и начала математического анализа 10 класс Алимов Задание 548

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\[1)\sin\frac{47\pi}{6} = \sin\left( 8\pi - \frac{\pi}{6} \right) =\]

\[= \sin\left( - \frac{\pi}{6} \right) = - \sin\frac{\pi}{6} = - \frac{1}{2}\]

\[2)\ tg\frac{25\pi}{4} = tg\left( 6\pi + \frac{\pi}{4} \right) =\]

\[= \text{tg}\frac{\pi}{4} = 1\]

\[3)\ ctg\frac{27\pi}{4} = ctg\ \left( 7\pi - \frac{\pi}{4} \right) =\]

\[= \text{ctg\ }\left( - \frac{\pi}{4} \right) = - ctg\frac{\pi}{4} = - 1\]

\[4)\cos\frac{21\pi}{4} = \cos\left( 4\pi + \frac{5\pi}{4} \right) =\]

\[= \cos\frac{5\pi}{4} = \cos\left( \pi + \frac{\pi}{4} \right) =\]

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