Задание 14.5

Question

${ }^{\circ}$ Вычислите значение тригонометрической функции:
1) $\cos 225^{\circ}$
2) $\sin 240^{\circ}$
3) $\cos \frac{5 \pi}{4}$
4) $\cos \left(-\frac{4 \pi}{3}\right)$.

Gimli · Accepted Answer

\begin{enumerate}
\item $$\cos 225^{\circ}=\cos \left(180^{\circ}+45^{\circ}\right)=-\cos 45^{\circ}$$
\item $$\sin 240^{\circ}=\sin \left(180^{\circ}+60^{\circ}\right)=-\sin 60^{\circ}$$
\item $$\cos \frac{5 \pi}{4}=\cos \left(\pi+\frac{\pi}{4}\right)=-\cos \frac{\pi}{4}$$
\item $$\cos \left(-\frac{4}{3} \pi\right)=\cos \left(\pi+\frac{\pi}{3}\right)=-\cos \frac{\pi}{3}$$
\end{enumerate}

Задание 14.5

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Задание 14.5

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