The circle x2 + y2 – 2x – 2y + 1 = 0 is rolled along the positive direction of x - axis and makes one complete roll. Find its equation in new - position.
Given equation of the circle is x2 + y2 - 2x - 2y + 1 = 0.
We know that the equation of the circle with centre (p,q) and having radius ‘r’ is given by:
⇒ (x - p)2 + (y - q)2 = r2 ..... - (1)
Now,
⇒ x2 + y2 - 2x - 2y + 1 = 0
⇒ (x2 - 2x + 1) + (y2 - 2y + 1) = 1
⇒ (x - 1)2 + (y - 1)2 = (1)2 ..... (2)
Comparing (2) with (1), we get
⇒ Centre = (1,1) and radius = 1
It is told that the circle is rolled along the positive direction of x - axis and makes one complete roll.
We know that the complete roll of a circle covers the distance 2r, where r is the radius of the circle.
The centre of the circle as moves 2r in the positive direction of xthe - axis.
Let the d be the distance moved by the centre on completion of one roll.
⇒
⇒ d = 2
The new position of the centre is (1 + d,1)
⇒ Centre = (1 + 2π, 1)
We have circle with centre (1 + 2π, 1) and having radius 1 units.
We know that the equation of the circle with centre (p, q) and having radius ‘r’ is given by:
⇒ (x - p)2 + (y - q)2 = r2
Now we substitute the corresponding values in the equation:
⇒ (x - (1 + 2π))2 + (y - 1)2 = 12
⇒ (x - 1 - 2π)2 + (y - 1)2 = 1
⇒ x2 - (2 + 4π)x + (1 + 2π)2 + y2 - 2y + 1 = 1
⇒ x2 + y2 - (2 + 4π)x - 2y - (1 + 2π)2 = 0
∴The equations of the circles is x2 + y2 - (2 + 4π)x - 2y - (1 + 2π)2 = 0.