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JEE Advanced 2012Paper 2
Exam
JEE Advanced
Year
2012
Paper
Paper 2
Subject
Mathematics
Chapter
Circle

JEE Advanced 2012 · Paper 2 · Mathematics · Circle

A tangent P T is drawn to the circle x^ 2 +y^ 2 =4 at the point P(...

A tangent PTP T is drawn to the circle x2+y2=4x^{2}+y^{2}=4 at the point P(3,1)P(\sqrt{3}, 1). A straight line LL, perpendicular to PTP T is a tangent to the circle (x−3)2+y2−1(x-3)^{2}+y^{2}-1. Question: A possible equation of LL is

Options

  1. Ax−3y=1x-\sqrt{3} y=1
  2. Bx+3y=1x+\sqrt{3} y=1
  3. Cx−3y=−1x-\sqrt{3} y=-1
  4. Dx+3y=5x+\sqrt{3} y=5

Correct answer

A. x−3y=1x-\sqrt{3} y=1

Step-by-step solution

Equation of tangent PTP T to the circle x2+y2=4x^{2}+y^{2}=4 at the point P(3,1)P(\sqrt{3}, 1) is x3+y=4x \sqrt{3}+y=4 Let the line LL, perpendicular to tangent PTP T be x−y3+λ=0x-y \sqrt{3}+\lambda=0 As it is tangent to the circle (x−3)2+y2=1∴(x-3)^{2}+y^{2}=1 \therefore \quad Length of perpendicular from centre of circle to the Tangent = radius of circle. ⇒∣3+λ2∣=1⇒λ=−1 or −5∴\Rightarrow\left|\frac{3+\lambda}{2}\right|=1 \Rightarrow \lambda=-1 \text{ or }-5 \therefore Equation of LL can be x−3y=1x-\sqrt{3} y=1 or x−3y=5x-\sqrt{3} y=5
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