Soal persamaan trigonometri nomor 7

2 cos (2x - 60°) = 1
cos (2x - 60°) = 1/2
cos (2x - 60°) = cos 60°
2x - 60° = 60° ± k . 360°
2x = 120° + k.360°
x = 60° + k.180°
x1 = 60° + 0.180° = 60°

cos (2x - 60°) = cos 300°
2x - 60° = 300° ± k.360°
2x = 360° ± k.360°
x = 180° + k.180°
x2 = 180° + 0.180° = 180°
x3 = 180° + 1.180° = 360°
x3 = 0°

HP = {0°, 60°, 180°}