Question

и cos x cos - sin x sin

Answer 1

Ответ:

21

1

-1/2

Объяснение:

$-3\sqrt[5]{(-7)^{5}}=-3(-7)=21$

$\frac{(2\sqrt{3})^2}{12}=\frac{4*3}{12}=\frac{12}{12}=1$

$cos\frac{\pi}{12} x cos\frac{7\pi}{12} - sin\frac{\pi}{12} x sin\frac{7\pi}{12}=\\=cos(\frac{\pi}{12}+\frac{7\pi}{12})=cos\frac{8\pi}{12}=cos\frac{2\pi}{3}=\\=cos 120^{0}= -\frac{1}{2}$