Q.

Let the curve z(1+i)+z¯(1–i)=4, z∈C, divide the region |z–3|≤1 into two parts of area α and β. Then |α–β| equals :          [2025]

1 1+π3  
2 1+π6  
3 1+π4  
4 1+π2  

Ans.

(4)

Let z = x + iy, then from given equation, we have

(x + iy)(1 + i) + (x – iy)(1 – i) = 4

⇒ x + ix + iy – y + x – ix – iy – y = 4

⇒ 2x – 2y = 4 ⇒ x – y = 2

Now, |z–3|≤1 ⇒ (x–3)2+y2≤1

β = Area of shaded region = π(1)24–12×1×1

                                           = (π4–12) sq. units

α = Area of unshaded region inside the circle

   =34π(1)2+12×1×1=(3π4+12) sq. units

 Now, |α–β| = difference of area

 = (3π4+12)–(π4–12)=π2+1.