Answer:
[tex]2 { \sin}^{2} \theta \: - \sin\theta - 1 = 0 \\ let \: \theta \: be \: x \\ = > 2 {x}^{2} - x - 1 = 0 \\ (x - 1)(2x + 1) = 0 \\ x = 1 \: or \: x = - 0.5 \\ therefore \: \sin\theta = 1 \: or \: \sin\theta = - 0.5 \\ \theta = \sin ^{ - 1} (1) \: \: or \: \: \theta = \sin {}^{ - 1} ( - 0.5) \\ \theta = 90 \degree \: or \: = 210\degree \: and \: 330\degree[/tex]
