Cos(5x-п/4)= - корень из 3/2

5x-π/4=+-5π/6+2πn,n∈z 5x=-7π/12+2πn,n∈z U 5x=13π/12+2πn,n∈z x=-7π/60+2πn/5,n∈z U x=13π/60+2πn/5,n∈z