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Value of sum(k = 1)^(100)(i^(k!) + omega...

Value of `sum_(k = 1)^(100)(i^(k!) + omega^(k!))`, where i = `sqrt(-1) and omega` is complex cube root of unity , is :

A

`190 + omega`

B

`192 + omega^(2)`

C

`190 + i`

D

192 + i

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to evaluate the sum: \[ S = \sum_{k=1}^{100} (i^{k!} + \omega^{k!}) \] where \(i = \sqrt{-1}\) and \(\omega\) is a complex cube root of unity. ### Step 1: Separate the summation We can separate the summation into two parts: \[ S = \sum_{k=1}^{100} i^{k!} + \sum_{k=1}^{100} \omega^{k!} \] ### Step 2: Evaluate \( \sum_{k=1}^{100} i^{k!} \) We start with the first summation: - For \(k=1\), \(i^{1!} = i\) - For \(k=2\), \(i^{2!} = i^{2} = -1\) - For \(k=3\), \(i^{3!} = i^{6} = (i^{4})i^{2} = 1 \cdot (-1) = -1\) - For \(k=4\), \(i^{4!} = i^{24} = (i^{4})^{6} = 1^{6} = 1\) Notice that \(i^{k!}\) will cycle through \(i, -1, -i, 1\) based on the value of \(k!\) modulo 4. For \(k \geq 4\), \(k!\) is always a multiple of 4, which means \(i^{k!} = 1\). Thus, we can summarize: - \(k = 1: i\) - \(k = 2: -1\) - \(k = 3: -1\) - \(k \geq 4: 1\) (for \(k = 4\) to \(100\)) Counting the contributions: - From \(k=4\) to \(100\) gives \(97\) terms of \(1\). - Total contribution from \(k=4\) to \(100\) is \(97 \cdot 1 = 97\). So the total for the first summation is: \[ i - 1 - 1 + 97 = i + 95 \] ### Step 3: Evaluate \( \sum_{k=1}^{100} \omega^{k!} \) Next, we evaluate the second summation: The complex cube roots of unity satisfy: \[ \omega^3 = 1 \quad \text{and} \quad 1 + \omega + \omega^2 = 0 \] - For \(k=1\), \(\omega^{1!} = \omega\) - For \(k=2\), \(\omega^{2!} = \omega^{2}\) - For \(k=3\), \(\omega^{3!} = \omega^{6} = 1\) For \(k \geq 4\), \(k!\) is also a multiple of 3, so \(\omega^{k!} = 1\). Thus, we can summarize: - \(k = 1: \omega\) - \(k = 2: \omega^{2}\) - \(k = 3: 1\) - \(k \geq 4: 1\) (for \(k = 4\) to \(100\)) Counting the contributions: - From \(k=4\) to \(100\) gives \(97\) terms of \(1\). - Total contribution from \(k=4\) to \(100\) is \(97 \cdot 1 = 97\). So the total for the second summation is: \[ \omega + \omega^{2} + 1 + 97 = 0 + 97 = 97 \] ### Step 4: Combine the results Now we combine the results from both summations: \[ S = (i + 95) + 97 = i + 192 \] ### Final Answer Thus, the value of the summation is: \[ \boxed{i + 192} \]

To solve the problem, we need to evaluate the sum: \[ S = \sum_{k=1}^{100} (i^{k!} + \omega^{k!}) \] where \(i = \sqrt{-1}\) and \(\omega\) is a complex cube root of unity. ...
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