JEE Main & Advanced Mathematics Conic Sections Question Bank Hyperbola

  • question_answer
    The locus of the point of intersection of any two perpendicular tangents to the hyperbola is a circle which is called the director circle of the hyperbola, then the eqn  of this circle is 

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

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

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

    D)            None of these

    Correct Answer: B

    Solution :

               Equation of hyperbola is \[\frac{{{x}^{2}}}{{{a}^{2}}}-\frac{{{y}^{2}}}{{{b}^{2}}}=1\]            Any tangent to hyperbola are \[y=mx\pm \sqrt{{{a}^{2}}{{m}^{2}}-{{b}^{2}}}\]            Also tangent perpendicular to this is \[y=\frac{-1}{m}x\pm \sqrt{\frac{{{a}^{2}}}{{{m}^{2}}}-{{b}^{2}}}\]                    Eliminating m, we get \[{{x}^{2}}+{{y}^{2}}={{a}^{2}}-{{b}^{2}}\].


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