MCQ
If $z=\frac{1-i \sqrt{3}}{1+i \sqrt{3}}$, then $\arg (z)=$
  • A
    $60^{\circ}$
  • B
    $120^{\circ}$
  • $240^{\circ}$
  • D
    $300^{\circ}$

Answer

Correct option: C.
$240^{\circ}$
(C)
$\arg \left(\frac{1-i \sqrt{3}}{1+i \sqrt{3}}\right)=\arg (1-i \sqrt{3})-\arg (1+i \sqrt{3})$
$=-60^{\circ}-60^{\circ}=-120^{\circ}$ or $240^{\circ}$
$\ldots\left[\begin{array}{c}\because \arg (1- i \sqrt{3})=-\tan ^{-1} \sqrt{3}=-60^{\circ} \\ \text { and } \arg (1+ i \sqrt{3})=\tan ^{-1} \sqrt{3}=60^{\circ}\end{array}\right]$

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