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Question: Answered & Verified by Expert
$A\left(z_1=2+2 i\right), B\left(z_2\right), C\left(z_3\right)$ are three points on the Argand plane satisfying $\left|z_k-2 i\right|=2,(k=1,2,3)$. If $\triangle A B C$ encloses the maximum area, then the sum of the imaginary parts of $z_2$ and $z_3$ is
MathematicsComplex NumberTS EAMCETTS EAMCET 2020 (11 Sep Shift 1)
Options:
  • A 1
  • B 0
  • C 4
  • D -4
Solution:
1225 Upvotes Verified Answer
The correct answer is: 4
According to given information $|z-2 i|=2$ is a circle having centre is $(0,2)$ and radius is 2 .


If the area of $\triangle A B C$ is maximum the triangle must be equilateral triangle and point $M$ is the mid point of $B C$, where $M$ is the foot of perpendicular of point $A\left(z_1=2+2 i\right)$ on $B C$.
$\therefore$ Sum of the imaginary parts of $z_2$ and $z_3$ is twice of the imaginary part of $M=2 \times 2=4$.

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