сos2x=0
2x=П/2(2k+1)
x=П/4(2k+1)
|x-1,6|>=0
|П/4(2k+1)-1,6|>=0
П(2k+1)<=6,4
2k+1<=6,4/П
2k<=1
k<1/2 k-целое
k=0 x=П/4
1/4<1/y<1/2,
¹⁰/₉ или 1.(1)