Question

Kerjakan no 15 beserta caranya!!!

Answer 1

Cos (x + 2/3 π) - cos (x - 2/3 π) = 1/2 √3
=> cos (x + 120°) - cos (x - 120°) = 1/2 √3
=> -2 sin [(x + 120°)+(x - 120°)]/2 sin [(x + 120°)-(x - 120°)]/2 = 1/2 √3
=> -2 sin x sin 120° = 1/2 √3
=> -2 sin x . 1/2√3 = 1/2 √3
=> -2 sin x = 1
=> sin x = -1/2
sin x bernilai negatif di kuadran 3 dan 4
sin x = 1/2 => x = 30°
kuadran 3 : x = (180 + 30) = 210° = 7/6 π
kuadran 4 : x = (360 - 30) = 330° = 11/6 π