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TS EAMCET · Maths · Circle

If the line \(a x+b y=1\) is a tangent to the circle \(s_r \equiv x^2+y^2-r^2=0\), then which one of the following is true?

  1. A \((a, b)\) lies on the circle \(S_1=0\)
  2. B \((a, b)\) lies inside the circle \(S_{1 / 2}=0\)
  3. C \((a, b)\) lies outside the circle \(S_2=0\)
  4. D \((a, b)\) lies on the circle \(S_3=0\)
Verified Solution

Answer & Solution

Correct Answer

(A) \((a, b)\) lies on the circle \(S_1=0\)

Step-by-step Solution

Detailed explanation

We have, \(a x+b y=1\) is tangent of circle \(x^2+y^2-r^2=0\) \( \therefore \quad r=\frac{1}{\sqrt{a^2+b^2}} \Rightarrow r^2=\frac{1}{a^2+b^2} \Rightarrow a^2+b^2=\frac{1}{r^2} \) \(r=1,(a, b)\) lie on the circle \(\therefore(a, b)\) lie on the circle when \(S_1=0\)