The general value $\theta $ is obtained from the equation $\cos 2\theta = \sin \alpha ,$ is
The general value $\theta $ is obtained from the equation $\cos 2\theta = \sin \alpha ,$ is
- A
$2\theta = \frac{\pi }{2} - \alpha $
- B
$\theta = 2n\pi \pm \left( {\frac{\pi }{2} - \alpha } \right)$
- C
$\theta = \frac{{n\pi + {{( - 1)}^n}\alpha }}{2}$
- D
$\theta = n\pi \pm \left( {\frac{\pi }{4} - \frac{\alpha }{2}} \right)$
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