JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2009

  • question_answer
        If\[\alpha ,\beta ,\gamma \in \left[ 0,\frac{\pi }{2} \right],\] then  the  value of \[\frac{\sin (\alpha +\beta +\gamma )}{sin\text{ }\alpha +sin\,\beta +sin\text{ }\gamma }\]is

    A)  \[<1\]                                  

    B)  \[=-1\]

    C)  \[<0\]                                  

    D)  None of these

    Correct Answer: A

    Solution :

                    We have,\[sin\text{ }\alpha +sin\,\,\beta +sin\text{ }\gamma -sin\text{ }(\alpha +\beta +\gamma )\] \[=sin\text{ }\alpha +sin\text{ }\beta +sin\text{ }\gamma -sin\alpha \text{ }cos\beta \text{ }cos\gamma \]           \[-cos\text{ }\alpha \text{ }sin\text{ }\beta \text{ }cos\text{ }\gamma -cos\text{ }\alpha \text{ }cos\text{ }\beta \text{ }sin\text{ }\gamma \]    \[+\text{ }sin\text{ }\alpha \text{ }sin\text{ }\beta \text{ }sin\text{ }\gamma \] \[=\sin \alpha (1-\cos \beta \cos \gamma )+\sin \beta (1-\cos \alpha \cos \gamma )\] \[+\sin \gamma (1-\cos \alpha \cos \beta )+\sin \alpha \sin \beta \sin \gamma \] \[\therefore \] \[\sin \alpha +\sin \beta +\sin \gamma >\sin (\alpha +\beta +\gamma )\] \[\Rightarrow \]               \[\frac{\sin (\alpha +\beta +\gamma )}{\sin \alpha +\sin \beta +\sin \gamma }<1\]


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