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JEE Main & Advanced Mathematics Complex Numbers and Quadratic Equations Question Bank De Moivre's theorem and Roots of unity

  • question_answer
    If \[\cos \alpha +\cos \beta +\cos \gamma =0=\]\[\sin \alpha +\sin \beta +\sin \gamma \] then \[\cos 2\alpha +\cos 2\beta +\cos 2\gamma \] equals [RPET 2000]

    A) \[2\cos (\alpha +\beta +\gamma )\]

    B) \[\cos 2(\alpha +\beta +\gamma )\]

    C) 0

    D) 1

    Correct Answer: C

    Solution :

    See solution of above question.


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