Question

Пожалуйста решите,это очень важно!!!!!

Answer 1

$\displaystyle\bf\\Cos(\pi -\alpha )=-\frac{\sqrt{2} }{2} \\\\\\-Cos\alpha =-\frac{\sqrt{2} }{2} \\\\\\Cos\alpha =\frac{\sqrt{2} }{2} \\\\\\\alpha =\pm arc Cos\frac{\sqrt{2} }{2} +2\pi n ,n\in Z\\\\\\\alpha =\pm \frac{\pi }{4}+2\pi n,n\in Z$