Question:

If \(z\) and \(\omega\) are two complex numbers such that
\(|z\omega|=1\)
and
\(\arg(z)-\arg(\omega)=\frac{3\pi}{2}\)
, then
\(\arg\left(\frac{1-2\overline{z}\omega}{1+3\overline{z}\omega}\right)\)
is :
(Here \(\arg(z)\) denotes the principal argument of complex number \(z\))

Show Hint

Show that \(\overline{z}\omega=i\) (modulus 1, argument \(-\frac{3\pi}{2}\equiv\frac{\pi}{2}\)) and then find the argument of \(\frac{1-2i}{1+3i}\).
Updated On: Nov 4, 2026
  • \(\frac{\pi}{4}\)
  • \(-\frac{3\pi}{4}\)
  • \(-\frac{\pi}{4}\)
  • \(\frac{3\pi}{4}\)
Show Solution
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The Correct Option is B

Solution and Explanation

\(|\overline z\omega|=|z\omega|=1\) and \(\arg(\overline z\omega)=\arg\omega-\arg z=-\frac{3\pi}{2}\), so \(\overline z\omega=e^{-3\pi i/2}=i\).
\(\frac{1-2i}{1+3i}=\frac{(1-2i)(1-3i)}{10}=\frac{1-3i-2i+6i^2}{10}=\frac{-5-5i}{10}=-\frac{1+i}{2}\).
This lies in the third quadrant, with principal argument \(-\pi+\frac\pi4=-\frac{3\pi}{4}\).
Answer: (2) \(-\frac{3\pi}{4}\)
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