г) $4\sqrt{2}\cos\dfrac{\pi}{4}\cos\dfrac{7\pi}{3}$

Question

Вопрос: $Фото задания: г) $4\sqrt{2}\cos\dfrac{\pi}{4}\cos\dfrac{7\pi}{3}$$ Фото задания

Accepted Answer

$\cos\dfrac{\pi}{4}=\dfrac{\sqrt{2}}{2}$, а $\cos\dfrac{7\pi}{3}=\cos\left(2\pi+\dfrac{\pi}{3}\right)=\dfrac12$.

$4\sqrt{2}\cdot\dfrac{\sqrt{2}}{2}\cdot\dfrac12=2$.

Ответ: 2.

г) \(4\sqrt{2}\cos\dfrac{\pi}{4}\cos\dfrac{7\pi}{3}\)