KVPY Sample Paper KVPY Stream-SX Model Paper-1

  • question_answer
    The angle \[\alpha ,\]\[\beta ,\]\[\gamma \] of a triangle satisfy the equation \[2\sin \alpha +3\cos \beta =3\sqrt{2}\] and \[3\sin \beta +2\cos \alpha =1.\] Then, \[\gamma \] equal

    A) \[150{}^\circ \]            

    B) \[120{}^\circ \]

    C) \[60{}^\circ \]                          

    D) \[30{}^\circ \]

    Correct Answer: D

    Solution :

    [d]
    Given,
    \[2\sin \alpha +3\cos \beta =3\sqrt{2}\]                ... (i)
    \[3\sin \beta +2\cos \alpha =1\]               ... (ii)
    On squaring and adding Eqs. (i) and (ii),
    we get
    \[4+9+12\,(\sin \alpha \cos \beta +\sin \beta \cos \alpha )=18+1\]
    \[\Rightarrow \]\[12\sin \,(\alpha +\beta )=6\]
    \[\Rightarrow \]\[\sin \,(\alpha +\beta )=\frac{1}{2}\]
    \[\Rightarrow \]\[\alpha +\beta =150{}^\circ \]
    \[\Rightarrow \]\[\alpha +\beta \ne 30{}^\circ \]
    \[\therefore \]\[\gamma =180-(\alpha +\beta )\]
    \[\Rightarrow \]\[\gamma =30{}^\circ \]


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