tentukan hasil dan caranya

2 cos²x - 3 cos x + 1 = 0

misal cos x = a

2a² - 3a + 1 = 0
(2a - 1)(a - 1) = 0

2a - 1 = 0
2a = 1
a = 1/2

dan

a - 1 = 0
a = 1

cos x = 1/2
x = 60° = π/3
dan
x = 300° = 5π/3

cos x = 1
x = 0 (tidak memenuhi karena 0 < x < 2π)
dan
x = 360° = 2π (tidak memenuhi karena 0 < x < 2π)

Jawaban D