You can put this solution on YOUR website! What is 2cos^2 θ + cosθ -1=0 using the interval 0 ≤ θ < 2 π?
**
2cos^2 θ + cosθ -1=0
(2cosθ+1)(cosθ-1)=0
2cosθ+1=0
2cosθ=-1
cosθ=-1/2
θ=2π/3 and 4π/3 (in quadrants II and III where cos<0)
or
cosθ-1=0
cosθ=1
θ=0
ans:
θ=0, 2π/3, and 4π/3
(