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JEE Advanced · Mathematics · 17. Properties of Triangles

Paragraph:
Consider the circle \(x^2+y^2=9\) and the parabola \(y^2=8 x\). They intersect at \(P\) and \(Q\) in the first and the fourth quadrants, respectively. Tangents to the circle at \(P\) and \(Q\) intersect the \(\mathrm{X}\)-axis at \(R\) and tangents to the parabola at \(P\) and \(Q\) intersect the \(\mathrm{X}\)-axis at \(S\).Question:
The radius of the incircle of the \(\triangle P Q R\) is

  1. A
    4
  2. B
    3
  3. C
    \(\frac{8}{3}\)
  4. D
    2
Verified Solution

Answer & Solution

Correct Answer

(D)
2

Step-by-step Solution

Detailed explanation

Radius of incircle is, \(r=\frac{\Delta}{s}\)
As \(\Delta=16 \sqrt{2}\)
\[
\begin{aligned}
& \therefore \quad s=\frac{6 \sqrt{2}+6 \sqrt{2}+4 \sqrt{2}}{2}=8 \sqrt{2} \\
& \therefore \quad r=\frac{16 \sqrt{2}}{8 \sqrt{2}}=2 \\
&
\end{aligned}
\]
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