Sin² x+ Sin²2x = Sin²3x
Sin² x - Sin²3x + Sin²2x = 0
(Sinx - Sin3x)(Sinx+Sin3x) + Sin2x = 0
-2SinxCos2x*2Sin2xCosx + Sin2x = 0
-Sin2x*Sin4x + Sin2x = 0
Sin2x(-Sin4x +1) = 0
Sin2x = 0 или -Sin4x +1 = 0
2x = πn, n ∈Z Sin4x = 1
x = πn/2, n ∈Z 4x = π/2 + πk , k ∈Z
x = π/8 + πk/2 , k ∈Z