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For a positive integer n, find the value of ( 1 − i ) n ( 1 − 1 i ) n .

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Question

For a positive integer n, find the value of \[(1 - i )^n \left( 1 - \frac{1}{i} \right)^n\].

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Solution

\[(1 - i )^n \left( 1 - \frac{1}{i} \right)^n = \left( 1 - i \right)^n \left( 1 - \frac{i^4}{i} \right)^n [ \because i^4 = 1]\]

\[ = \left( 1 - i \right)^n \left( 1 - i^3 \right)^n \]

\[ = \left( 1 - i \right)^n \left( 1 + i \right)^n [ \because i^3 = - i]\]

\[ = \left[ (1 - i)(1 + i) \right]^n \]

\[ = (1 - i^2 )^n \]

\[ = 2^n [ \because i^2 = - 1]\]

Thus, the value of 

\[(1 - i )^n \left( 1 - \frac{1}{i} \right)^n\] is 2n.

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Chapter 13: Complex Numbers - Exercise 13.2 [Page 32]

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R.D. Sharma Mathematics [English] Class 11
Chapter 13 Complex Numbers
Exercise 13.2 | Q 17 | Page 32

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