Question

Срочно нужен cos(3ㅠ/4)=

Answer 1

$cos \frac{3 \pi }{4} =cos( \frac{4 \pi - \pi }{4} )=cos( \frac{4 \pi }{4} - \frac{ \pi }{4})=cos( \pi - \frac{ \pi }{4} )= -cos \frac{ \pi }{4} =- \frac{ \sqrt{2} }{2}$