JEE Main & Advanced Mathematics Rectangular Cartesian Coordinates Question Bank Transformation of axes and Locus

  • question_answer
    The equation to the locus of a point which moves so that its distance from x-axis is always one half its distance from the origin, is  

    A) \[{{x}^{2}}+3{{y}^{2}}=0\]

    B) \[{{x}^{2}}-3{{y}^{2}}=0\]

    C) \[3{{x}^{2}}+{{y}^{2}}=0\]

    D) \[3{{x}^{2}}-{{y}^{2}}=0\]

    Correct Answer: B

    Solution :

    Let the moving point be (x, y) and its distance from x-axis is y. Therefore, according to given condition \[\frac{1}{2}\sqrt{{{x}^{2}}+{{y}^{2}}}=y\,\,\,\Rightarrow \,\,{{x}^{2}}-3{{y}^{2}}=0\] This is required locus of the point (x, y).


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