CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2000

  • question_answer
    From the origin, chords are drawn to the circle\[{{x}^{2}}+{{y}^{2}}-2y=0\]. The locus of the middle points of these chords is:

    A)  \[{{x}^{2}}+{{y}^{2}}-y=0\]

    B)  \[{{x}^{2}}+{{y}^{2}}-x=0\]

    C)  \[{{x}^{2}}+{{y}^{2}}-2x=0\]

    D)  \[{{x}^{2}}+{{y}^{2}}-x-y=0\]

    E)  \[{{x}^{2}}+{{y}^{2}}+y=0\]

    Correct Answer: A

    Solution :

    Let\[(h,k)\]be the midpoint of the chord drawn through the origin. Then the equation of the chord is \[hx+ky-(y+k)={{h}^{2}}+{{k}^{2}}-2k\] This passes through (0, 0) \[\therefore \] \[-k={{h}^{2}}+{{k}^{2}}-2k\] \[\Rightarrow \]               \[{{h}^{2}}+{{k}^{2}}-k=0\] \[\therefore \]Locus of\[(h,k)\]is\[{{x}^{2}}+{{y}^{2}}-y=0\].


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