3cosx-2sin^2=-3 ,0

[tex]3cosx-2 sin^{2}x=-3 \\ 3cosx-(2-2 cos^{2} x)+3=0 \\ 2 cos^{2}x+3cosx+1 = 0 \\ (cosx+1)(2cosx+1) = 0[/tex]
cosx = -1 ∨ cosx= -1/2

∴ cosx=-1
→ x = 180°+k.360°
*k=0
 x = 180°+0.360°
 x = 180°
*k=1
 x = 180°+1.360°
 x = 440° (tidak memenuhi)
→ x = -180°+k.360°
*k=0
x = -180°+0.360°
x = -180° (tidak memenuhi)
*k=1
x = -180°+1.360°
x = 180°
*k=2
x = -180°+2.360°
x = 540° (tidak memenuhi)

∴ cosx=-1/2
→ x = 120°+k.360°
*k=0
x = 120°+0.360°
x = 120°
*k=1
x = 120°+1.360°
x = 480° (tidak memenuhi)
→ x = -120°+k.360°
*k=0
x = -120°+0.360°
x = -120° (tidak memenuhi)
*k=1
x = -120°+1.360°
x = 240°
*k=2
x = -120°+2.360°
x = 600° (tidak memenuhi)

∴HP = { 120°,180°,240° }

Semoga membantu, jadikan yg terbaik ya ....