cos(п+x)=корень2/2 cos(x-3\п)=1

$1) \ cos(\pi+x) = \frac{\sqrt{2}}{2}\\ \pi+x = +-arccos\frac{\sqrt{2}}{2} + 2\pi n , \ \ neZ\\ \pi+x = +-\frac{{\pi}}{4} + 2\pi n , \ \ neZ\\ x1 = \frac{{\pi}}{4} -\pi + 2\pi n , \ \ neZ\\ x1 = - \frac{{3\pi}}{4} + 2\pi n , \ \ neZ\\ \\ x2 = - \frac{{\pi}}{4} -\pi + 2\pi n , \ \ neZ\\ x2 = - \frac{{5\pi}}{4} + 2\pi n , \ \ neZ\\$

$2)cos(x-\frac{3}{\pi})=1\\ x-\frac{3}{\pi} = 2\pi n , \ \ neZ\\ x=\frac{3}{\pi} +2\pi n , \ neZ\\$