You want to find values of [tex]\theta[/tex] where that equation is true. You can do this by solving the equation. First: [tex]-1-2 \cos{\theta} = -1[/tex] [tex]-2 \cos{\theta} = 0[/tex] [tex]\cos{\theta} = 0[/tex] For what values of [tex]\theta[/tex] is the cosine function 0? Hint: look at the graph of cosine
