JEE Main & Advanced Mathematics Conic Sections Question Bank Ellipse

  • question_answer
    The equation of normal at the point (0, 3) of the ellipse \[9{{x}^{2}}+5{{y}^{2}}=45\] is    [MP PET 1998]

    A)            \[y-3=0\]                                   

    B)            \[y+3=0\]

    C)            x-axis                                         

    D)            y-axis

    Correct Answer: D

    Solution :

               For \[\frac{{{x}^{2}}}{{{a}^{2}}}+\frac{{{y}^{2}}}{{{b}^{2}}}=1,\] equation of normal at point\[({{x}_{1}},{{y}_{1}})\],                    Þ\[\frac{(x-{{x}_{1}}){{a}^{2}}}{{{x}_{1}}}=\frac{(y-{{y}_{1}}){{b}^{2}}}{{{y}_{1}}}\];  \\[({{x}_{1}},{{y}_{1}})\equiv (0,3),\,\,{{a}^{2}}=5,\,\,{{b}^{2}}=9\]                    \[\Rightarrow \frac{(x-0)}{0}\,\,\,5=\frac{(y-3).9}{3}\] or \[x=0\] i.e., y-axis.


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