RAJASTHAN ­ PET Rajasthan PET Solved Paper-2003

  • question_answer
    \[\frac{d}{dx}{{\cosh }^{-1}}(\sec x)\]is equal to

    A)  \[sin\text{ }x\]             

    B)  \[sec\text{ }x\]

    C)  \[tan\text{ }x\]             

    D)  \[cosec\text{ }x\]

    Correct Answer: B

    Solution :

     \[\frac{d}{dx}{{\cosh }^{-1}}(\sec x)\] \[=\frac{1}{\sqrt{{{\sec }^{2}}x-1}}.\sec x\tan x\] \[\left[ \because \frac{d}{dx}{{\cosh }^{-1}}x=\frac{1}{\sqrt{{{x}^{2}}-1}} \right]\] \[=\frac{\sec x.\tan x}{\sqrt{{{\tan }^{2}}x}}\] \[=\frac{\sec x.\tan x}{\tan x}\] \[=\sec x\]


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