JEE Main & Advanced JEE Main Paper (Held On 8 April 2017)

  • question_answer
    If\[S=\left\{ x\in [0,2\pi ]:\left| \begin{matrix}    0 & \cos x & -\sin x  \\    \sin x & 0 & \cos x  \\    \cos x & \sin x & 0  \\ \end{matrix} \right|=0 \right\},\] Then \[\sum\limits_{x\in S}^{{}}{\tan }\left( \frac{\pi }{3}+x \right)\] [JEE Online 08-04-2017]

    A) \[4+2\sqrt{3}\]                 

    B) \[-2-\sqrt{3}\]

    C) \[-2+\sqrt{3}\]                 

    D) \[-4-2\sqrt{3}\]

    Correct Answer: B

    Solution :

    \[0(0-cosx)-cosx(0-co{{s}^{2}}x)-sinx\]\[(si{{n}^{2}}x-0)=0\]\[{{\cos }^{3}}x-{{\sin }^{3}}x=0\]\[{{\tan }^{3}}=1\Rightarrow \tan x=1\]                 \[\sum\limits_{{}}^{{}}{\frac{\sqrt{3}+\tan x}{1-\sqrt{3}}}\] \[\sum\limits_{{}}^{{}}{\frac{\sqrt{3}+1}{1-\sqrt{3}}\times \frac{1+\sqrt{3}}{1+\sqrt{3}}}\Rightarrow \sum\limits_{{}}^{{}}{\frac{1+3+2\sqrt{3}}{-2}=}\sum\limits_{{}}^{{}}{\frac{{{4}^{2}}}{-2}-\frac{2\sqrt{3}}{3}}\]\[\sum\limits_{{}}^{{}}{-2-\sqrt{3}}\]           


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