√3sin 2x + cos5x = cos9x
cos9x-cos5x=-2sin7x*cos2x
sqrt(3)cos2x=2sin7x*cos2x
sqrt(3)cos2x - 2 sin7x*cos2x=0
cos2x*(sqrt(3)-2sin7x)=0
cos2x=0
2x=(π/2) +πn , n ∈ Z
x=(π/4)+(π/2)*n, n ∈ Z
или
sqrt(3)-2sin7x=0
sin7x=sqrt(3)/2
7x=(-1)^(k)*(π/3)+πk, k ∈ Z
x=(-1)^(k)*(π/21)+(π/7)k, k ∈ Z
О т в е т.(π/4)+(π/2)*n, n ∈ Z; (-1)^(k)*(π/21)+(π/7)k, k ∈ Z