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If (1-i1+i)100 = a + ib, then find (a, b).

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Question

If `((1 - i)/(1 + i))^100` = a + ib, then find (a, b).

Sum
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Solution

We have `((1 - i)/(1 + i))^100` = a + bi

⇒ `((1 - i)/(1 + i) xx (1 - i)/(1 - i))^100` = a + bi

⇒ `((1 + i^2 - 2i)/(1 - i^2))^100` = a + bi

⇒ `((1 - 1 - 2i)/(1 + 1))^100` = a + bi

⇒ `((-2i)/2)^100` = a + bi

⇒ (–i)100 = a + bi

⇒ i100 = a + bi

⇒ (i4)25 = a + bi

⇒ (1)25 = a + bi

⇒ 1 = a + bi

⇒ 1 + 0i = a + bi

Comparing the real and imaginary parts,

We have a = 1, b = 0

Hence (a, b) = (1, 0)

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Chapter 5: Complex Numbers and Quadratic Equations - Exercise [Page 91]

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NCERT Exemplar Mathematics Exemplar [English] Class 11
Chapter 5 Complex Numbers and Quadratic Equations
Exercise | Q 5 | Page 91

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