Sinx + Sin5x - Sin3x = 0
2Sin3xCos2x - sin3x = 0
Sin3x(2Cos2x - 1) = 0
Sin3x = 0 или 2Cos2x -1 = 0
3x = πn, n Є Z 2Cos2x = 1
x = πn/3, n Є Z Cos2x = 1/2
2x = +-arcCos1/2 + 2πk, kЄ Z
2x =+-π/3 + 2πk, kЄ Z
x = +-π/6 + 2πk/3, kЄ Z
Ответ: x = +-π/6 + 2πk/3, kЄ Z