Question

Mohon dibantu yah !!

Answer 1

2cos^2x-cosx-1=0
(2cosx+1)(cosx-1)=0 maka
2cosx+1=0 dan cosx -1=0
2cosx=-1 cos x = 1
cosx=-1/2 x = 0, 360
x = 120, 240
jadi x yg memenuhi 0,120,240,360