KVPY Sample Paper KVPY Stream-SX Model Paper-30

  • question_answer
    Let \[\Delta =\left| \begin{matrix}    \sin \theta \cos \phi  & \sin \theta \sin \phi  & \cos \theta   \\    \cos \theta \cos \phi  & \cos \theta \sin \phi  & -\sin \theta   \\    -\sin \theta \sin \phi  & \sin \theta \cos \phi  & 0  \\ \end{matrix} \right|\], then

    A) \[\Delta \] is independent of \[\theta \]

    B) \[\Delta \] is independent of \[\phi \]

    C) \[\Delta \] is a constant

    D) none of these

    Correct Answer: B

    Solution :

    \[\Delta =\left| \begin{matrix}    \sin \theta \cos \phi  & \sin \theta \sin \phi  & \cos \theta   \\    \cos \theta \cos \phi  & \cos \theta \sin \phi  & -\sin \theta   \\    -\sin \theta \sin \phi  & \sin \theta \cos \phi  & 0  \\ \end{matrix} \right|\]
    \[\Delta ={{\sin }^{2}}\theta \cos \theta \left| \begin{matrix}    \cos \phi  & \sin \phi  & \cot \theta   \\    \cos \phi  & \sin \phi  & -\tan \theta   \\    -\sin \phi  & \cos \phi  & 0  \\ \end{matrix} \right|\]
    \[\Delta =\sin \theta \]


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