CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2004

  • question_answer
    If \[y={{\tan }^{-1}}(\sec \,x-\tan x)\], then \[\frac{d\,y}{d\,x}\] is equal to:

    A)  2                                            

    B)  -2

    C)  \[\frac{1}{2}\]                                  

    D)  \[\frac{d\,y}{d\,x}\]

    Correct Answer: D

    Solution :

    We have, \[y={{\tan }^{-1}}\,(\sec x-\tan x)\]                 \[\frac{dy}{dx}=\frac{d}{dx}{{\tan }^{-1}}\left( \frac{1-\sin x}{\cos x} \right)\]                 \[\frac{dy}{dx}=\frac{d}{dx}{{\tan }^{-1}}\left( \frac{\sin \left( \frac{x}{2} \right)-\cos \left( \frac{x}{2} \right)}{\cos \left( \frac{x}{2} \right)-\sin \left( \frac{x}{2} \right)} \right)\]                                 \[=\frac{d}{dx}\left( \frac{\pi }{4}-\frac{x}{2} \right)\]                                 \[=-1/2\]


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