Let a circle C 1 be obtained on rolling the circle x 2 + y 2 - 4 x - 6 y + 11 = 0 upwards 4 units on the…

Let a circle C1 be obtained on rolling the circle x2+y2-4x-6y+11=0 upwards 4 units on the tangent T to it at the point 3,2. Let C2 be the image of C1 in T. Let A and B be the centers of circles C1 and C2 respectively, and M and N be respectively the feet of perpendiculars drawn from A and B on the x-axis. Then the area of the trapezium AMNB is:
  1. 22+2
  2. 41+2
  3. 3+22
  4. 21+2

Solution

We have,

x2+y2-4x-6y+11=0

x-22+y-32=2

Centre2,3

Radius r=2 units

Equation of tangent at 3,2 is

3x+2y-2x+3-3y+2+11=0

x=y=1   ...1

On rolling the given circle upward 4 units on the tangent 1, centre of the circle also moving 4 unit upward, so

 

 

Centre of C1 is

=2+22,3+22

A2+22,3+22

Centre of C2 is

B4+22,1+22

So, M2+22,0 and N4+22,0.

  area of trapezium

=12AM+BN×MN

=124+422=41+2 sq. units

Asked in: JEE Main 2023 (31 Jan Shift 1)

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