CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2005

  • question_answer
    If\[y={{\tan }^{-1}}\left( \frac{a\cos x-b\sin x}{b\cos x+a\sin x} \right),\]then\[\frac{dy}{dx}\]is equal to:

    A)  2                                            

    B)  \[-1\]

    C)  \[\frac{a}{b}\]                 

    D)         0

    E)  \[\frac{b}{a}\]

    Correct Answer: B

    Solution :

    \[y={{\tan }^{-1}}\left( \frac{a\cos x-b\sin x}{b\cos x+a\sin x} \right)\] \[={{\tan }^{-1}}\left( \frac{\frac{a}{b}-\tan x}{1+\frac{a}{b}\tan x} \right)\] \[={{\tan }^{-1}}\left\{ \tan \left( {{\tan }^{-1}}\left( \frac{a}{b} \right)-x \right) \right\}\] \[\Rightarrow \]               \[y={{\tan }^{-1}}\left( \frac{a}{b} \right)-x\] On differentiating w.r.t.,\[x,\]we get                 \[\frac{dy}{dx}=0-1=-1\]


You need to login to perform this action.
You will be redirected in 3 sec spinner