Manipal Engineering Manipal Engineering Solved Paper-2008

  • question_answer
    The most general solutions of the equation\[\sec x-1=(\sqrt{2}-1)\tan x\]are given by

    A) \[n\pi +\frac{\pi }{8}\]                  

    B) \[2n\pi ,\,\,2n\pi +\frac{\pi }{4}\]

    C) \[2n\pi \]                            

    D)         None of these

    Correct Answer: B

    Solution :

    Given,                 \[\sec x-1=(\sqrt{2}-1)\tan x\] \[\Rightarrow \]               \[1-\cos x=(\sqrt{2}-1)\sin x\] \[\Rightarrow \]               \[\sin \frac{x}{2}\left( \sin \frac{x}{2}-(\sqrt{2}-1)\cos \frac{x}{2} \right)=0\] \[\Rightarrow \]\[\sin \frac{x}{2}=0\]                                                                   or            \[\tan \frac{x}{2}=\sqrt{2}-1=\tan \frac{{{45}^{o}}}{2}\] \[\Rightarrow \]               \[\frac{x}{2}=n\pi \]or\[\frac{x}{2}=n\pi +\frac{\pi }{8}\] \[\Rightarrow \]               \[x=2n\pi ,\,\,2n\pi +\frac{\pi }{4}\]


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