Question

третье задание пожалуйста

Answer 1

Ответ:

$\displaystyle -\frac{\sqrt{3} }{2} ;\\\\\\\frac{\sqrt{2} }{2}$

Объяснение:

$\displaystyle cos\bigg(-\frac{19\pi }{6} \bigg)=cos\bigg(\frac{19\pi }{6} \bigg)=cos \bigg(2\pi +\frac{7\pi }{6} \bigg)=cos\bigg(\frac{7\pi }{6} \bigg)=-\frac{\sqrt{3} }{2}$

$\displaystyle sin\bigg(-\frac{21\pi }{4} \bigg)=-sin \bigg(\frac{21\pi }{4} \bigg)=-sin \bigg(4\pi +\frac{5\pi }{4} \bigg)=-sin\bigg(\frac{5\pi }{4} \bigg)=-\bigg(-\frac{\sqrt{2} }{2} \bigg)=\\\\\\=\frac{\sqrt{2} }{2}$