Корень( Cos 2xCos 5x) = Cos2x | ^2
Cos2x Cos5x = Cos^2 2x
Cos2x Cos 5x - Cos^2 2x = 0
Cox 2x(Cos 5x -Cos 2x) = 0
Cos 2x = 0 или Сos5x -Cos 2x = 0
2x = π/2 + πk , k ЄZ -2Sin3,5x Sin1,5x = 0
x = π/4 + πk/2 , k ЄZ Sin3,5x = 0 или Sin1,5x = 0
3,5x = πn, n ЄZ 1,5x = πm, m ЄZ
x = 2πn/7 , n ЄZ x = 2πm/3, m ЄZ