Tolong bantuin dong kak, nomor 9 – 11, pakai cara yaa, terima kasihh

Nomor 9

2cos² x + √3sin 2x = 1 + √3
cos 2x +1 + √3sin 2x = 1 + √3
cos 2x + √3sin 2x = √3

k = √(1² + (√3)²) = 2
tan α = √3
α = π/3

Persamaan diatas dapat dirubah menjadi:
2 cos (2x – π/3) = √3
cos (2x – π/3) = 1/2 √3
cos (2x – π/3) = cos (π/6)
2x – π/3 = π/6 + k.2π          atau    2x – π/3 = -π/6 + k.2π
         2x = π/2 + k.2π                             2x = π/6 + k.2π
           x = π/4 + k.π                                  x = π/12 +k.π
k =0 → x = π/4                            k =0 → x = π/12   

HP = { π/12, π/4}    (D)

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Nomor 10

2cos x + 2 sin x = √2
cos x + sin x =1/2√2

k = √2
tan α = 1
α = 45°

√2cos(x – 45°) = 1/2√2
cos(x – 45°) = 1/2
cos (x – 45) = cos 60
x – 45 = 60 + k.360        atau  x – 45 = – 60 + k.360
x = 105 + k.360                          x = – 15 + k.360
k = 0 → x = 105°               k = 1 → x = 345°

Hp = {105°, 345°}   (D)

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Nomor 11
√3 cos x + sin x = √2

k = 2
tan α = π/6

2cos (x – π/6) = √2
cos (x – π/6) = 1/2 √2
cos (x – π/6) = cos π/4
x – π/6 = π/4 + k.2π           atau x – π/6 = – π/4 + k.2π
x = 5π/12  + k.2π                                 x = -π/12 + k.2π
k = 0 → x = 5π/12             k = 1 →      x = 23π/12

Hp = {5π/12, 23π/12}      (E)