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SSC Sample Paper Mock Test-8 SSC CGL Tear-II Paper-1

  • question_answer
    \[\sin \,\,(n+1)A\,\,\sin \,\,(n-1)\,\,A+\cos \,\,(n+1)\,\,A\,\,\cos \,\,(n-1)\,\,A\]equal to

    A)  \[\sin 2A\]

    B)  \[\cos 2A\]

    C)  \[\tan 2A\]

    D)  \[\cot 2A\]

    Correct Answer: B

    Solution :

    \[\sin \,\,(n+1)A\sin \,\,(n-1)A+\cos \,\,(n+1)A\cos \,\,(n-1)A\] \[=\cos \,\,(n+1)A\cos \,\,(n-1)A+\sin \,\,(n+1)A\sin \,\,(n-1)A\]\[=\cos \,\,[(n+1)A-\,\,(n-1)A]=\cos \,\,[nA+A-nA+A]\]\[=\cos 2A\]


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