CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2007

  • question_answer
    The parametric representation of a point on the ellipse whose foci are (3, 0) and\[(-1,\text{ }0)\] and eccentricity 2/3 is

    A)  \[(1+3\text{ }cos\text{ }\theta ,\text{ }\sqrt{3}sin\theta )\]

    B)  \[(1+3\text{ }cos\theta ,\text{ }5\text{ }sin\theta )\]

    C)  \[(1+3\text{ }cos\theta ,1+\sqrt{5}sin\theta )\]

    D)  \[(1+3\text{ }cos\theta ,1+5\text{ }sin\theta )\]

    E)  \[(1+3cos\theta ,\sqrt{5}sin\theta )\]

    Correct Answer: E

    Solution :

    Given that, foci are (3, 0) and\[(-1,0)\] and\[e=\frac{2}{3}\] \[\therefore \]  \[2ae=4\] \[\Rightarrow \]               \[2\times a\times \frac{2}{3}=4\Rightarrow a=3\] Also, \[e=\sqrt{1-\frac{{{b}^{2}}}{{{a}^{2}}}}\Rightarrow \frac{4}{9}=1-\frac{{{b}^{2}}}{9}\] \[\Rightarrow \] \[\frac{{{b}^{2}}}{9}=1-\frac{4}{9}=\frac{5}{9}\Rightarrow b=\sqrt{5}\] \[\therefore \]Parametric representation of a point is\[(1+3\cos \theta ,\sqrt{5}\sin \theta ).\]


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