Manipal Engineering Manipal Engineering Solved Paper-2011

  • question_answer
    A circle touches the x-axis and also touches the circle which centre at (0, 3) and radius 2, The locus of the centre of the circle is

    A)  a parabola        

    B)  a circle

    C)  an ellipse         

    D)         a hyperbola

    Correct Answer: A

    Solution :

    Let the centre of a circle be\[{{C}_{1}}(h,\,\,k)\] Since,    \[{{C}_{1}}{{C}_{2}}={{r}_{1}}+{{r}_{2}}\]                               (given) \[\Rightarrow \]               \[\sqrt{{{(h-0)}^{2}}+{{(k-3)}^{2}}}=|k+2|\] \[\Rightarrow \]               \[{{h}^{2}}=5(2k-1)\] Hence, locus of a point is\[{{x}^{2}}=5(2y-1)\]which represents\[\text{a}\]equation of parabola.


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