જો $\cos \,(\theta - \alpha ) = a,\,\,\sin \,(\theta - \beta ) = b,\,\,$ તો ${\cos ^2}(\alpha - \beta ) + 2ab\,\sin \,(\alpha - \beta )  = . . . .$

  • A

    $4{a^2}{b^2}$

  • B

    ${a^2} - {b^2}$

  • C

    ${a^2} + {b^2}$

  • D

    $ - {a^2}{b^2}$

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