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AP EAMCET · Maths · Circle

If \(\theta\) is the angle between the tangents drawn from the point \((-1,-1)\) to the circle \(x^2+y^2-4 x-6 y+c=0\) and \(\cos \theta=-\frac{7}{25}\), then the radius of the circle is

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

Answer & Solution

Correct Answer

(A) \(4\)

Step-by-step Solution

Detailed explanation

Center of circle: \( (2,3) \) Distance from center to \((-1,-1)\): \(d = \sqrt{(2-(-1))^2 + (3-(-1))^2} = \sqrt{3^2+4^2} = \sqrt{25} = 5 \) Given \(\cos \theta = -\frac{7}{25}\), and \(\cos \theta = 2\left(\frac{L}{d}\right)^2 - 1 \), where \(L\) is the length of the tangent.…
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