Question

Ada yang bisa bantu No 3-5?

Answer 1

Verified answer

3) 3 cos 2x + 5 sin x + 1 = 0
3 (1 - 2 sin²x) + 5 sin x + 1 = 0
3 - 6 sin²x + 5 sin x + 1 = 0
6 sin²x - 5 sin x - 4 = 0
(3 sin x - 4) (2 sin x + 1) = 0
3 sin x = 4 atau 2 sin x = - 1
sin x = 4/3 ( tdk mungkin) atau
sin x = - ½ mk x1 = 210° = 7π/6 dan x2 = 330°= 11π/6 (jwban A)

4) cos 2x + 7sin x - 4 = 0
1 - 2 sin²x + 7 sin x - 4 = 0
2 sin²x - 7 sin x + 3 = 0
(2sin x - 1)(sin x - 3) = 0
2 sin x = 1 atau sin x = 3 (tdk mungkin)
sin x = ½ mk x1 = 30° dan x2 = 150° ( jwban E)

5) √3 sin 2x + 2 cos²x = - 1
√3 (2 sin x cos x) + 2 cos²x + 1 = 0
2 cos²x + 2√3 sin x cos x + (sin²x + cos²x) = 0
3 cos²x + 2√3 sin x cos x + sin²x = 0
(√3 cos x + sin x)² = 0
√3 cos x + sin x = 0
sin x = - √3 cos x (bagi dgn cos x)
tan x = - √3 mk x1 = 120° dan x2 = 300° ( jwban D)