J & K CET Engineering J and K - CET Engineering Solved Paper-2010

  • question_answer
    If the straight lines \[2x-3y+1=0\] and \[4x-6y+5=0\] are tangents to the same circle, then the radius of the circle is

    A)  \[\frac{3}{2\sqrt{13}}\]

    B)  \[\frac{3}{4\sqrt{13}}\]

    C)  \[\frac{3}{8\sqrt{13}}\]

    D)  \[2\]

    Correct Answer: B

    Solution :

    Given, straight lines are \[2x-3y+1=0\] and    \[4x-6y+5=0\] or \[2x-3y+\frac{5}{2}=0\] Which re parallel. Since, these lines are the tangents of a circle, therefore distance d between these lines is the diameter of the circle. \[\therefore \] \[d=\left| \frac{\frac{5}{2}-1}{\sqrt{4+9}} \right|=\frac{3}{2\sqrt{13}}\] \[\therefore \] Radius of the circle is\[\frac{3}{4\sqrt{13}}\].


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