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JEE Main20207 Jan 2020Evening ShiftMathematicsCircleActual

Let the tangents drawn from the origin to the circle, x 2 + y 2 - 8 x - 4 y + 16 = 0 touch it at the points A and B . Then A B 2 is equal to

Options

  1. A52 5
  2. B56 5
  3. C64 5
  4. D32 5

Correct answer

C. 64 5

Step-by-step solution

L = S 1 = 16 = 4 R = 16 + 4 - 16 = 2 Length of chord of contact = 2 L R L 2 + R 2 = 2 × 4 × 2 16 + 4 = 16 20

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