cos3x+cos5x+sqrt(2)cos4x=0
2cos4xcosx+sqrt(2)cos4x=0
cos4x(2cosx+sqrt(2))=0
cos4x=0
x=П/8(2k+1)
П/2<=П/8(2k+1)<=П
3<=2k<=7
k=2 k=3 x=5П/8 x=7П/8
сosx=-sqrt(2)/2
x=3П/4
cos3x+cos5x+sqrt(2)cos4x=0
2cos4xcosx+sqrt(2)cos4x=0
cos4x(2cosx+sqrt(2))=0
cos4x=0
x=П/8(2k+1)
П/2<=П/8(2k+1)<=П
3<=2k<=7
k=2 k=3 x=5П/8 x=7П/8
сosx=-sqrt(2)/2
x=3П/4