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Question: Answered & Verified by Expert
If the lines \(3 x-4 y+4=0\) and \(6 x-8 y-7=0\) are tangents to a circle, then the radius of the circle is
MathematicsCircleBITSATBITSAT 2011
Options:
  • A \(3 / 2\)
  • B \(3 / 4\)
  • C \(1 / 10\)
  • D \(1 / 20\)
Solution:
2052 Upvotes Verified Answer
The correct answer is: \(3 / 4\)
The diameter of the circle is perpendicular distance between the parallel lines (tangents) \(3 x-4 y+4=0\) and \(3 x-4 y-\frac{7}{2}=0\) and so it is equal to
\(\frac{4}{\sqrt{9+16}}+\frac{7 / 2}{\sqrt{9+16}}=\frac{3}{2}\). Hence radius is \(\frac{3}{4}\)

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