यदि $\sin \theta  + \sin 2\theta  + \sin 3\theta  = \sin \alpha $ तथा $\cos \theta  + \cos 2\theta  + \cos 3\theta  = \cos \alpha $, तब $\theta$  का मान होगा

  • A

    $\alpha /2$

  • B

    $\alpha $

  • C

    $2\alpha $

  • D

    $\alpha /6$

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  • [IIT 1988]

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