JEE Main & Advanced Mathematics Conic Sections Question Bank Ellipse

  • question_answer
    Equation of the ellipse with eccentricity \[\frac{1}{2}\] and foci at \[(\pm 1,\ 0)\] is        [MP PET 2002]

    A)            \[\frac{{{x}^{2}}}{3}+\frac{{{y}^{2}}}{4}=1\]                                

    B)            \[\frac{{{x}^{2}}}{4}+\frac{{{y}^{2}}}{3}=1\]

    C)            \[\frac{{{x}^{2}}}{3}+\frac{{{y}^{2}}}{4}=\frac{4}{3}\]                

    D)            None of these

    Correct Answer: B

    Solution :

               Given that, \[e=\frac{1}{2}\] and \[(\pm \,ae,\,0)=\,(\pm \,1,\,0)\]            \[\Rightarrow \,ae=1\] \[\Rightarrow a=2\]. Now \[{{b}^{2}}={{a}^{2}}(1-{{e}^{2}})\]            \[\Rightarrow \,\,\,{{b}^{2}}=4\left( 1-\frac{1}{4} \right)\]\[\Rightarrow \,\,{{b}^{2}}=3\]            Hence, equation of ellipse is \[\frac{{{x}^{2}}}{4}+\frac{{{y}^{2}}}{3}=1.\]


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