Answer:
π, 2π/3, 4π/3
Step-by-step explanation:
2cos²(x)+3cos(x)+1=0
1) Lets give cos x=y
So, we can rewrite our equation
2y²+3y+1=0
(2y+1)(y+1)=0
2y+1=0 or y+1=0
2y+1=0, 2y= -1 , y = -1/2
y+1=0, y= - 1
2) cos(x)= - 1, x=π
cos(x)= - 1/2, x=2π/3 or 4π/3
