RAJASTHAN ­ PET Rajasthan PET Solved Paper-2002

  • question_answer
    If the lines\[3x-4y+4=0\]and\[6x-8y-7=0\]are the tangents of a circle, then radius of the circle is

    A)  \[\frac{3}{2}\]

    B)  \[\frac{3}{4}\]

    C)  \[\frac{1}{10}\]

    D)  \[\frac{1}{20}\]

    Correct Answer: B

    Solution :

     Since, given lines are parallel. Thus, diameter of the circle is the distance between the tangents\[3x-4y+4=0\]and \[3x-4y-\frac{7}{2}=0\]Since, these lines are in opposite direction. Thus, distance between these lines \[=\frac{4}{\sqrt{9+16}}+\frac{7/2}{\sqrt{9+16}}\] \[=\frac{4}{5}+\frac{7}{10}=\frac{15}{10}=\frac{3}{2}\] Hence, radius\[=\frac{1}{2}\](length of diameter) \[=\frac{1}{2}\left( \frac{3}{2} \right)=\frac{3}{4}\]


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