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Statement -1 : The expression ((2i)/(1+i...

Statement -1 : The expression `((2i)/(1+i))^(n)` is a positive integer for all the values of n.
and
Statement -2 : Here n=8 is the least positive for which the above expression is a positive integer.

A

Statement -1 is True, Statement -2 is True, Statement -2 is a correct explanation for statement -6

B

Statement -1 is True, Statement -2 is True , Statement -2 is NOT a correct explanation for Statement -6

C

Statement -1 is True, Statement -2 is False

D

Statement -1 is Flase, Statement -2 is True

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to analyze the two statements regarding the expression \(\left(\frac{2i}{1+i}\right)^n\). ### Step 1: Simplifying the Expression We start with the expression: \[ \frac{2i}{1+i} \] To simplify this, we can multiply the numerator and the denominator by the conjugate of the denominator: \[ \frac{2i(1-i)}{(1+i)(1-i)} = \frac{2i - 2i^2}{1^2 - i^2} = \frac{2i + 2}{1 + 1} = \frac{2 + 2i}{2} = 1 + i \] Thus, we have: \[ \frac{2i}{1+i} = 1 + i \] ### Step 2: Raising to the Power \(n\) Now, we need to evaluate: \[ (1+i)^n \] To determine if this expression is a positive integer for all \(n\), we can express \(1+i\) in polar form. The modulus of \(1+i\) is: \[ |1+i| = \sqrt{1^2 + 1^2} = \sqrt{2} \] The argument (angle) \(\theta\) is: \[ \theta = \tan^{-1}\left(\frac{1}{1}\right) = \frac{\pi}{4} \] Thus, we can write: \[ 1+i = \sqrt{2} \left(\cos\frac{\pi}{4} + i\sin\frac{\pi}{4}\right) \] Using De Moivre's theorem, we can express \((1+i)^n\) as: \[ (1+i)^n = (\sqrt{2})^n \left(\cos\frac{n\pi}{4} + i\sin\frac{n\pi}{4}\right) = 2^{n/2} \left(\cos\frac{n\pi}{4} + i\sin\frac{n\pi}{4}\right) \] ### Step 3: Analyzing the Result For \((1+i)^n\) to be a positive integer, the imaginary part must be zero, and the real part must be positive. This occurs when: \[ \sin\frac{n\pi}{4} = 0 \quad \text{and} \quad \cos\frac{n\pi}{4} > 0 \] The sine function is zero when: \[ \frac{n\pi}{4} = k\pi \quad \text{for } k \in \mathbb{Z} \implies n = 4k \] The cosine function is positive when: \[ \frac{n\pi}{4} \in (-\frac{\pi}{2}, \frac{\pi}{2}) \quad \text{or } \frac{n}{4} \in (0, 1) \implies n \in (0, 4) \] Thus, the smallest positive integer \(n\) that satisfies both conditions is \(n=8\). ### Conclusion - **Statement 1** is false because \((1+i)^n\) is not a positive integer for all \(n\). - **Statement 2** is true because \(n=8\) is indeed the least positive integer for which \((1+i)^n\) is a positive integer.
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