MCQ
The general value of $\theta $ satisfying ${\sin ^2}\theta + \sin \theta = 2$ is
  • A
    $n\pi + {( - 1)^n}\frac{\pi }{6}$
  • B
    $2n\pi + \frac{\pi }{4}$
  • $n\pi + {( - 1)^n}\frac{\pi }{2}$
  • D
    $n\pi + {( - 1)^n}\frac{\pi }{3}$

Answer

Correct option: C.
$n\pi + {( - 1)^n}\frac{\pi }{2}$
c
(c) ${\sin ^2}\theta + \sin \theta - 2 = 0$

$\Rightarrow (\sin \theta - 1)\,(\sin \theta + 2) = 0$

$ \Rightarrow $ $\sin \theta \ne - 2$ ,

$\therefore \,\,\sin \theta = 1 = \sin \pi /2$

$ \Rightarrow $ $\theta = n\pi + {( - 1)^n}\frac{\pi }{2}$.

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