JCECE Engineering JCECE Engineering Solved Paper-2012

  • question_answer
    The eccentricity of an ellipse whose pair of a conjugate diameter are \[y=x\] and \[3y=-2x\] is

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

    B) \[\frac{1}{3}\]

    C) \[\frac{1}{\sqrt{3}}\]                                     

    D)  None of these

    Correct Answer: C

    Solution :

    Let the ellipse be\[\frac{{{x}^{2}}}{{{a}^{2}}}+\frac{{{y}^{2}}}{{{b}^{2}}}=1\]. Since,\[y=x\] and \[3y=-2x\] is a pair of conjugate diameters. Therefore,                 \[{{m}_{1}}{{m}_{2}}=-\frac{{{b}^{2}}}{{{a}^{2}}}\] \[\Rightarrow \]               \[(1)\left( -\frac{2}{3} \right)=-\frac{{{b}^{2}}}{{{a}^{2}}}\] \[\Rightarrow \]               \[2{{a}^{2}}=3{{b}^{2}}\] \[\Rightarrow \]               \[2{{a}^{2}}=3{{a}^{2}}(1-{{e}^{2}})\] \[\Rightarrow \]               \[2=3(1-{{e}^{2}})\] \[\Rightarrow \]               \[{{e}^{2}}=\frac{1}{3}\] \[\Rightarrow \]               \[e=\frac{1}{\sqrt{3}}\]


You need to login to perform this action.
You will be redirected in 3 sec spinner