Answer:
[tex] \cos \: 2 \theta = \frac{1}{2} \\ \\ \therefore \: \cos \: 2 \theta = \cos \: 60 \degree \\ \therefore \: \cos \: 2 \theta = \cos \: (180 \degree - 120\degree ) \\ ( \because \: \theta \: lies \: between \: - 90 \degree \: and \: 90 \degree)\\ \therefore \: \cos \: 2 \theta = - \cos \: 120 \degree \\ \therefore \: 2 \theta = - 120 \degree \\ \therefore \: \theta = \frac{ - 120 \degree}{2} \\ \huge \red{\therefore \: \theta}\pink {= } \orange{ - 60 \degree}[/tex]
