## anonymous 2 years ago solve the equation. Give a general formula for all the solutions. 2 cosθ + 1 = 0

1. anonymous

$2\cos \theta+1=0$ $2\cos \theta= -1$ $\cos \theta=-\frac{ 1 }{ 2 }$ $\cos \theta=-\cos \frac{ \pi }{ 3 }$ $\cos \theta=\cos(\pi+\frac{ \pi }{ 3 })$ $\theta=2n \pi \pm \frac{ \pi }{ 3 }$ ...where $n \epsilon I$

2. anonymous

The answer choice are A.) θ=3π/2+kπ B.) θ=2π/3+2kπ, θ=4π/3+2kπ C.) θ=π/2+2kπ, θ=3π/2+2kπ D.) θ=2π/3+kπ, θ=4π/3+kπ

3. anonymous

hey sry I was wrong in last step $\theta=2n \pi+\frac{ 4\pi }{ 3 }$..........(1) and $\theta=2n \pi-\frac{ 4\pi }{ 3 }$ ........(2) where nϵI now put n=k in equation 1 and n= k+1 in equation 2 you will get the answer

4. anonymous

That's fine. Thank you so much ^^