JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2005

  • question_answer
        The equation of the ellipse whose foci are \[(\pm ,2,0)\]and eccentricity\[\frac{1}{2}\]is:

    A)  \[\frac{{{x}^{2}}}{12}+\frac{{{y}^{2}}}{16}=1\]

    B)  \[\frac{{{x}^{2}}}{16}+\frac{{{y}^{2}}}{12}=1\]

    C)  \[\frac{{{x}^{2}}}{16}+\frac{{{y}^{2}}}{8}=1\]

    D)  none of these

    Correct Answer: B

    Solution :

                    Let the ellipse be \[\frac{{{x}^{2}}}{{{a}^{2}}}+\frac{{{y}^{2}}}{{{b}^{2}}}=1\] It is given that\[e=\frac{1}{2}\]and \[ae=2\] Therefore, \[a=4\] Now,     \[{{b}^{2}}={{a}^{2}}(1-{{e}^{2}})\] \[\Rightarrow \]               \[{{b}^{2}}=12\] Thus the required ellipse is\[\frac{{{x}^{2}}}{16}+\frac{{{y}^{2}}}{12}=1.\]


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