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The value of Sigma(k=1)^(99)(i^(k!)+omeg...

The value of `Sigma_(k=1)^(99)(i^(k!)+omega^(k!))` is (where, `i=sqrt(-1)` amd `omega` is non - real cube root of unity)

A

`190+omega`

B

`192+omega^(2)`

C

`190+i`

D

`102+i`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to evaluate the summation: \[ \Sigma_{k=1}^{99} (i^{k!} + \omega^{k!}) \] where \( i = \sqrt{-1} \) and \( \omega \) is a non-real cube root of unity. ### Step 1: Split the Summation We can split the summation into two parts: \[ \Sigma_{k=1}^{99} i^{k!} + \Sigma_{k=1}^{99} \omega^{k!} \] Let’s denote: \[ A = \Sigma_{k=1}^{99} i^{k!} \quad \text{and} \quad B = \Sigma_{k=1}^{99} \omega^{k!} \] ### Step 2: Calculate \( A = \Sigma_{k=1}^{99} i^{k!} \) Now, we will calculate \( A \): - For \( k = 1 \): \( i^{1!} = i^1 = i \) - For \( k = 2 \): \( i^{2!} = i^2 = -1 \) - For \( k = 3 \): \( i^{3!} = i^6 = (i^4)(i^2) = 1 \cdot (-1) = -1 \) - For \( k = 4 \): \( i^{4!} = i^{24} = (i^4)^6 = 1^6 = 1 \) For \( k \geq 4 \), \( k! \) is a multiple of 4, thus: \[ i^{k!} = (i^4)^{m} = 1 \quad \text{for some integer } m \] So, for \( k \geq 4 \), \( i^{k!} = 1 \). Now, we can summarize the contributions: - \( A = i + (-1) + (-1) + 1 + 1 + 1 + \ldots + 1 \) - The number of terms from \( k = 4 \) to \( k = 99 \) is \( 99 - 4 + 1 = 96 \). Thus: \[ A = i - 1 - 1 + 1 + 96 = i + 94 \] ### Step 3: Calculate \( B = \Sigma_{k=1}^{99} \omega^{k!} \) Now, we will calculate \( B \): Recall that \( \omega \) is a non-real cube root of unity, satisfying \( \omega^3 = 1 \) and \( 1 + \omega + \omega^2 = 0 \). - For \( k = 1 \): \( \omega^{1!} = \omega \) - For \( k = 2 \): \( \omega^{2!} = \omega^2 \) - For \( k = 3 \): \( \omega^{3!} = \omega^6 = (\omega^3)^2 = 1 \) - For \( k \geq 3 \), \( k! \) is a multiple of 3, thus \( \omega^{k!} = 1 \). So, we summarize the contributions: \[ B = \omega + \omega^2 + 1 + 1 + \ldots + 1 \] The number of terms from \( k = 3 \) to \( k = 99 \) is \( 99 - 3 + 1 = 97 \). Thus: \[ B = \omega + \omega^2 + 1 + 96 = 0 + 96 = 96 \] ### Step 4: Combine \( A \) and \( B \) Now, we can combine \( A \) and \( B \): \[ \Sigma_{k=1}^{99} (i^{k!} + \omega^{k!}) = A + B = (i + 94) + 96 = i + 190 \] ### Final Answer The final value of the summation is: \[ \boxed{190 + i} \]
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