sin 2x =sin x 0 < x < 180°

sin 2x = sin x

2x = x + k.360°
x = k.360°

k = 0, x = 0° (tm)
k = 1, x = 360° (tm)

2x = 180 - x + k.360°
3x = 180 + k.360°
x = 60 + k.120°

k = 0, x = 60°

Hp = {60°}

sin 2x = sin x
2 sin x cos x = sin x
cos x = 1/2
x = 60°