J & K CET Engineering J and K - CET Engineering Solved Paper-2008

  • question_answer
    If  \[y={{\sec }^{-1}}\left( \frac{1}{\sqrt{1-{{x}^{2}}}} \right),\] then \[\frac{dy}{dx}\] is equal to

    A)  \[\frac{1}{\sqrt{1-{{x}^{2}}}}\]

    B)  \[\frac{2}{\sqrt{1-{{x}^{2}}}}\]

    C)  \[\frac{1}{\sqrt{1+{{x}^{2}}}}\]

    D)  \[\frac{2}{\sqrt{1+{{x}^{2}}}}\]

    Correct Answer: A

    Solution :

    Given,  \[y={{\sec }^{-1}}\left( \frac{1}{\sqrt{1-{{x}^{2}}}} \right)\] Put, \[x=\sin \theta \] \[\therefore \] \[y={{\sec }^{-1}}\left( \frac{1}{\sqrt{1-{{\sin }^{2}}\theta }} \right)\] \[\Rightarrow \] \[y={{\sec }^{-1}}(\sec \theta )=\theta \] \[\Rightarrow \] \[y={{\sin }^{-1}}x\] \[\Rightarrow \] \[\frac{dy}{dx}=\frac{1}{\sqrt{1-{{x}^{2}}}}\]


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