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Question: Answered & Verified by Expert
If the amplitude of $z-2-3 i$ is $\pi / 4$, then the locus of $z=x+i y$ is
MathematicsComplex NumberTS EAMCETTS EAMCET 2020 (14 Sep Shift 2)
Options:
  • A $x+y-1=0$
  • B $x-y-1=0$
  • C $x+y+1=0$
  • D $x-y+1=0$
Solution:
1309 Upvotes Verified Answer
The correct answer is: $x-y+1=0$
$\begin{aligned}
& \text { Given, } \arg (z-2-3 i)=\frac{\pi}{4} \Rightarrow z=x+i y \\
& z-2-3 i=x+i y-2-3 i=(x-2)+(y-3) i \\
& \arg (z-2-3 i)=\tan ^{-1}\left(\frac{y-3}{x-2}\right)=\frac{\pi}{4} \Rightarrow \frac{y-3}{x-2}=\tan \frac{\pi}{4} \\
& \quad y-3=x-2 \Rightarrow x-y+1=0
\end{aligned}$
$\therefore$ Locus of $z$ is $x-y+1=0$.

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