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JEE Mains · Maths · STD 11 - 10.1 circle and system of circle

Two tangents are drawn from a point \(P\) to the circle \(x^{2}+y^{2}-2 x-4 y+4=0\), such that the angle between these tangents is \(\tan ^{-1}\left(\frac{12}{5}\right)\), where \(\tan ^{-1}\left(\frac{12}{5}\right) \in(0, \pi)\). If the centre of the circle is denoted by \(C\) and these tangents touch the circle at points \(A\) and \(B\), then the ratio of the areas of \(\Delta PAB\) and \(\Delta CAB\) is :

  1. A \(11:4\)
  2. B \(9:4\)
  3. C \(3:1\)
  4. D \(2:1\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(9:4\)

Step-by-step Solution

Detailed explanation

\(\tan \theta=\frac{12}{5}\) \(PA =\cot \frac{\theta}{2}\) \(\therefore\) area of \(\Delta PAB =\frac{1}{2}( PA )^{2} \sin \theta=\frac{1}{2} \cot ^{2} \frac{\theta}{2} \sin \theta\) \(=\frac{1}{2}\left(\frac{1+\cos \theta}{1-\cos \theta}\right) \sin \theta\)…
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