JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2008

  • question_answer
        The derivative of\[{{a}^{\sec x}}\]w.r.t.\[{{a}^{\tan x}}(a>0)\]is

    A)  \[\sec x{{a}^{\sec x-\tan x}}\]  

    B)  \[\sin x{{a}^{\tan x-\sec x}}\]

    C)  \[\sin x{{a}^{\sec x-\tan x}}\]                   

    D)  \[{{a}^{\sec x-\tan x}}\]

    Correct Answer: C

    Solution :

                    Let\[u={{a}^{\sec x}}\]and\[v={{a}^{\tan x}}\] On differentiating w.r.t.\[x,\]we get                 \[\frac{du}{dx}={{a}^{\sec x}}{{\log }_{e}}a.\sec x\tan x\] and        \[\frac{dv}{dx}={{a}^{\tan x}}{{\log }_{e}}a.{{\sec }^{2}}x\] \[\therefore \]  \[\frac{du}{dv}=\frac{{{a}^{\sec x}}{{\log }_{e}}a.\sec x\tan x}{{{a}^{\tan x}}{{\log }_{e}}a.{{\sec }^{2}}x}\]                 \[={{a}^{\sec x-\tan x}}\sin x\]


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