1. x≥0
2. -5 ≤5cosx≤5 -11 ≤5cosx-6≤-1
3. y(-x)= -sinx/(-x)+2=sinx/x+2
y(x)=y(-x) четная ф-я.
4. sinx=1/2 x=(-1)ⁿπ/6+πn n∈Z x∈[0;2π] x=π/6; 5/6π
cos2x=√2/2 2x=+-π/4+2πn x=+-π/8+πn n∈Z x∈[0;2π]
x=π/8; 7π/8; 9π/8; 15/8π
5. cosx≤-1/2 x≤+-5π/6+2πn n∈Z x∈[-2π;π]
x=-5π/6;5π/6;7π/6;-7π/6
6. (x-2)/4=sinπ/2=1 x-2=4 x=6
7. см. график x∈[-2π;0]
