JEE Main & Advanced Mathematics Circle and System of Circles Question Bank Equations of circle, Geometrical problems regarding circle

  • question_answer
    The locus of the centre of the circle which cuts a chord of length 2a from the positive x-axis and passes through a point on positive y-axis distant b from the origin is

    A)            \[{{x}^{2}}+2by={{b}^{2}}+{{a}^{2}}\]                   

    B)            \[{{x}^{2}}-2by={{b}^{2}}+{{a}^{2}}\]

    C)            \[{{x}^{2}}+2by={{a}^{2}}-{{b}^{2}}\]                     

    D)            \[{{x}^{2}}-2by={{b}^{2}}-{{a}^{2}}\]

    Correct Answer: C

    Solution :

               Here \[2\sqrt{{{g}^{2}}-c}=2a\Rightarrow {{g}^{2}}-{{a}^{2}}-c=0\].....(i)                     and it passes through (0, b), therefore                    \[{{b}^{2}}+2fb+c=0\]                                                   ?.(ii)                       On adding (i) and (ii), we get \[{{g}^{2}}+2fb={{a}^{2}}-{{b}^{2}}\]                    Hence locus is \[{{x}^{2}}+2by={{a}^{2}}-{{b}^{2}}\] .


You need to login to perform this action.
You will be redirected in 3 sec spinner