ПОМОГИТЕ ПОЖАЛУЙСТА срочно 22.54(б,в)

Cos(π/4 - x) lt; √2/2

π/4 - 2πk lt; π/4 - x lt; 3π/4 - 2πk
- 2πk lt; -x lt; π/2 - 2πk
-π/2 + 2πk lt; x lt; 2πk, k∈Z

в) 
cos(3x -π/6) gt; -1/4; 0 ≤ arccos(-1/4) ≤ π
arccos(-1/4) + 2πk lt; 3x - π/6 lt; 2π - arccos(-1/4) +2πk
π/6 + arccos(-1/4) + 2πk lt; 3x lt; 2π + π/6 - arccos(-1/4) +2πk
π/18 + arccos(-1/4)/3 + 2πk/3 lt; x lt; 2π/3 + π/18 - arccos(-1/4)/3 +2πk/3, k∈Z