JEE Main & Advanced Mathematics Trigonometric Identities Question Bank Trigonometrical ratios of sum and difference of two and three angles

  • question_answer
    \[\sin (\beta +\gamma -\alpha )+\sin (\gamma +\alpha -\beta )\]\[+\sin (\alpha +\beta -\gamma )-\sin (\alpha +\beta +\gamma )=\]

    A) \[2\sin \alpha \sin \beta \sin \gamma \]

    B) \[4\sin \alpha \sin \beta \sin \gamma \]

    C) \[\sin \alpha \sin \beta \sin \gamma \]

    D) None of these

    Correct Answer: B

    Solution :

    Combine first two terms and last two terms L.H.S.\[=2\,\sin \gamma \cos \,(\beta -\alpha )+2\,\sin \,(-\gamma )\,\cos \,(\alpha +\beta )\]           \[=2\,\sin \,\gamma \,[\cos \,(\beta -\alpha )-\cos \,(\alpha +\beta )]\]          \[=2\,\sin \,\gamma \,.\,2\,\sin \alpha \,\sin \beta \]\[=4\sin \alpha \sin \beta \sin \gamma \].


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