Adalah
cos 2x + 3 sin x + 1 = 0
(1 – 2 sin²x) + 3 sin x + 1 = 0
2 sin² x – 3 sin x – 2 = 0
(2 sin x + 1)(sin x – 2) = 0
2 sin x + 1 = 0
2 sin x = -1
sin x = – 1
2
x = – 7 π + k . 2π ; k = 0 ➝ x = 7 π
6 6
atau
x = (π – 7 π) + k . 2π ; k = 1 ➝ x = 11 π
6 6
Jadi Hp = (7 π , 11 π)
6 6