(Sin9x -Sinx) + ( Sin3x - Sin7x) = 0
2Sin4x Cos5x - 2Sin2xCos5x = 0
Cos5x( Cos4x - Sin2x ) = 0
Cos5x = 0 или Cos4x - Sin2x = 0
5x = π/2 + πк, к ∈Z 1 - 2Sin²2x - Sin2x = 0
x = π/10 + πk / 5 , к ∈Z 2Sin²2x + Sin2x -1 = 0
а) Sinx = (-1 + 3)/4 = 1/2
х = (-1)^nπ/3 + nπ, n ∈Z
б) Sinx = -1
x = -π/2 + πm , m ∈Z