If the length of the tangent from any point on the circle x - 3 2 + y + 2 2 = 5 r 2 to the circle x - 3 2 +…

If the length of the tangent from any point on the circle x-32+y+22=5r2 to the circle x-32+y+22=r2 is 16 units, then the area between the two circles in sq. units is
  1. 32π
  2. 4π
  3. 8π
  4. 256π

Solution

Let point P(x1, y1) be any point on the circle, therefore it satisfies the circle

x1-32+y1+22=5r2....(i)

The length of the tangent drawn from point P(x1,y1) to the circle

x-32+y+22=r2 is S1

=x1-32+y1+22-r2

=5r2-r2 [from Eq. (i)]

=2r

Given that length of tangent is 16 units

  16=2r    r=8 units


The area between two circles is represented by shaded portion

So, area =π(5r2)-π(r2) =4πr2

=4π×82

=256π sq. units.

Asked in: AP EAMCET 2021 (19 Aug Shift 2)

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