KVPY Sample Paper KVPY Stream-SX Model Paper-11

  • question_answer
    If \[\int\limits_{0}^{\frac{\pi }{3}}{\frac{\tan \theta }{\sqrt{2k\sec \theta }}d\theta =1-\frac{1}{\sqrt{2}},\,(k>0),}\] then value of k is:

    A) 2

    B)

    C) 4

    D) 1

    Correct Answer: B

    Solution :

    \[\frac{1}{\sqrt{2k}}\int\limits_{0}^{\pi /3}{\frac{\tan \theta }{\sqrt{\sec \theta }}d\theta =\frac{1}{\sqrt{2k}}\int\limits_{0}^{\pi /3}{\frac{\sin \theta }{\sqrt{\cos \theta }}}}d\theta \]\[=\left. -\frac{1}{\sqrt{2k}}2\sqrt{\cos \theta } \right|_{0}^{\pi /3}\]\[=-\frac{\sqrt{2}}{\sqrt{k}}\left( \frac{1}{\sqrt{2}}-1 \right)\]  \[\Rightarrow \]   \[k=2.\]


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