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The Argument of 1 − I 1 + I is

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Question

The argument of \[\frac{1 - i}{1 + i}\] is

Options

  • \[- \frac{\pi}{2}\]

  • \[\frac{\pi}{2}\]

  • \[\frac{3\pi}{2}\]

  • \[\frac{5\pi}{2}\]

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Solution

\[- \frac{\pi}{2}\]

\[\text { Let } z = \frac{1 - i}{1 + i}\]

\[ \Rightarrow z=\frac{1 - i}{1 + i}\times\frac{1 - i}{1 - i}\]

\[ \Rightarrow z=\frac{1 + i^2 - 2i}{1 - i^2}\]

\[ \Rightarrow z = \frac{1 - 1 - 2i}{1 + 1}\]

\[ \Rightarrow z=\frac{- 2i}{2}\]

\[ \Rightarrow z= - i\]

\[\text { Since, z lies on negative direction of imaginary axis } . \]

\[\text { Therefore, } \arg (z) = \frac{- \pi}{2}\]

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Chapter 13: Complex Numbers - Exercise 13.6 [Page 66]

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R.D. Sharma Mathematics [English] Class 11
Chapter 13 Complex Numbers
Exercise 13.6 | Q 31 | Page 66

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