Question

Find a angles, 0°≤ theta < 360°, that solve the following equation.cos theta = -1

Answer 1

$\cos \theta=-1$

to solve the equation apply the inverse function of the cos on both sides

$\begin{gathered} \cos ^{-1}(\cos \theta)=\cos ^{-1}(-1) \\ \theta=\cos ^{-1}(-1) \\ \theta=180 \end{gathered}$

Using the unit circle there is only one solution over the given interval.

Answer

$\theta=180$