2cosx-1=0 и 2cosx+1=0 cosx=1\2 cosx=-1\2 x=7пи\6+2пиK x=11пи\6 +2пиK K целое
(√2 cosx-1)(2cosx+1)=0
√2 cosx-2 cosx+√2 cos2x+√2 -1=0
2√2 cos∧2 х+√2 cosx -2 cosx -1=0
х=2/3(3πn+-π), n ∈ Z
х=1/4(8πn+-π), n ∈ Z
