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Find the least positive integral value of n for which (1+i1−i)n is real.

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प्रश्न

Find the least positive integral value of n for which  \[\left( \frac{1 + i}{1 - i} \right)^n\] is real.

योग
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उत्तर

`((1+i)/(1-i))^n`

Simplify the base

`(1+i)/(1-i)`

`= ((1+i)(1+i))/((1-i)(1+i)) = (1+i)^2/(1^2-i^2)`

(1 + i)2 = 1 + 2i + i2 = 1 + 2i − 1 = 2i

12 − i2 = 1 − (−1) = 2

`(1+i)/(1-i) = (2i)/2 = i`

`((1+i)/(1-i))^n = i^n`

Find the least positive n

n = 2

n = 4 ...

n = 2

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अध्याय 13: Complex Numbers - Exercise 13.2 [पृष्ठ ३२]

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आर.डी. शर्मा Mathematics [English] Class 11
अध्याय 13 Complex Numbers
Exercise 13.2 | Q 9 | पृष्ठ ३२

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