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Write 1 − I in Polar Form.

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Question

Write 1 − i in polar form.

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Solution

\[z = 1 - i \]

\[r = \left| z \right|\]

\[ = \sqrt{1 + 1}\]

\[ = \sqrt{2}\]

\[\text { Let } \tan \alpha = \left| \frac{Im\left( z \right)}{Re\left( z \right)} \right|\]

\[ \therefore \tan\alpha = \left| \frac{- 1}{1} \right|\]

\[ = \frac{\pi}{4}\]

\[ \Rightarrow \alpha = \frac{\pi}{4}\]

\[\text { Since point  (1, - 1) lies in the fourth quadrant, the argument of z is given by } \]

\[\theta = - \alpha = - \frac{\pi}{4}\]

\[\text { Polar form = } r\left( \cos \theta + i\sin \theta \right) \]

\[ = \sqrt{2}\left\{ \cos\left( - \frac{\pi}{4} \right) + i\sin\left( - \frac{\pi}{4} \right) \right\}\]

\[ = \sqrt{2}\left( \cos\frac{\pi}{4} - i\sin\frac{\pi}{4} \right)\]

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Chapter 13: Complex Numbers - Exercise 13.5 [Page 62]

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R.D. Sharma Mathematics [English] Class 11
Chapter 13 Complex Numbers
Exercise 13.5 | Q 7 | Page 62

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