2 soal trigonometri jawab dan cara

18 -> maaf, tidak tau

19)

2sin^2 x – sinx – 1 = 0
misal = sin x = y

• 2y^2 – y – 1 = 0
• y^2 – y/2 – 1/2 = 0
• (y+1/2)(y-1) = 0
y = -1/2
y = 1

a) y = -1/2
sinx = -1/2
sin x = 210° atau sin x = 330°…..(1)

B) y = 1
sinx = 1
sin x = 90°……(2)

dri (1) dan (2), ddapat …
• Hp { 90°, 210°, 330° }
• Hp { (π/2) , (7π/6) , (11π/6) }