જો ${\cos ^6}\alpha + {\sin ^6}\alpha + K\,{\sin ^2}2\alpha = 1,$ તો $K =$

  • A

    $\frac{4}{3}$

  • B

    $\frac{3}{4}$

  • C

    $\frac{1}{2}$

  • D

    $2$

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  • [IIT 1986]

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