Manipal Engineering Manipal Engineering Solved Paper-2015

  • question_answer
    The    eccentricity    of    the    conic \[\underset{x\to -1}{\mathop{\lim }}\,\left( \frac{{{x}^{4}}+{{x}^{2}}=x+1}{{{x}^{2}}-x+1} \right)\frac{1-\cos (x+1)}{{{(x+1)}^{2}}}\]is

    A) \[\sqrt{\frac{2}{3}}\]                     

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

    C) \[{{e}^{1/2}}\]                  

    D) None of these

    Correct Answer: A

    Solution :

    We have,\[{{x}^{2}}-4x+4{{y}^{2}}=12\] \[\Rightarrow \]\[{{(x-2)}^{2}}+4{{(y-0)}^{2}}=8\] \[\Rightarrow \]\[\frac{{{(x-2)}^{2}}}{{{(2\sqrt{2})}^{2}}}+\frac{{{(y-0)}^{2}}}{(\sqrt{2})}=1\] which is an elhpse whose major and minor axes are \[2a=2\sqrt{2}\] and \[2b=\sqrt{2}\]repectively. \[\therefore \]Its eccentricity e is given by \[e=\sqrt{1-\frac{{{b}^{2}}}{{{a}^{2}}}}\] \[=\sqrt{1-\frac{2}{8}}=\frac{\sqrt{3}}{2}\]                


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