Question

Cos (-x/4)= - корень 2/2

Answer 1

$cos(-frac{x}4)=-frac{sqrt2}2\ -frac{x}4=бarccos (-frac{sqrt2}{2})+2pi n, neZ\ -frac{x}4=б(-frac{pi}4)+2pi n, neZ\ x=бpi+8pi n, neZ$