Question

решить уравнение cos²x-3cosx-4=0​

Answer 1

$Cos^{2}x-3Cosx-4=0\\\\\left[\begin{array}{ccc}Cosx=-1\\Cosx=4-neyd,-1\leq Cosx\leq1 \end{array}\right\\\\Cosx=-1\\\\x=\pi+2\pi n,n\in Z\\\\Otvet:\boxed{\pi+2\pi n,n\in Z}$