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Suppose omega!=1 is a sube root of unity...

Suppose `omega!=1` is a sube root of unity, and
`Delta=|(1,omega^(2),1-omega^(4)),(omega,1,1+omega^(5)),(1,omega,omega^(2))|` then `|Re(Delta)|=`_____________

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To solve the problem, we need to compute the determinant \( \Delta \) given by: \[ \Delta = \begin{vmatrix} 1 & \omega^2 & 1 - \omega^4 \\ \omega & 1 & 1 + \omega^5 \\ 1 & \omega & \omega^2 \end{vmatrix} \] where \( \omega \) is a cube root of unity, meaning \( \omega^3 = 1 \) and \( 1 + \omega + \omega^2 = 0 \). ### Step 1: Simplifying the Determinant First, we simplify the terms \( \omega^4 \) and \( \omega^5 \): - Since \( \omega^3 = 1 \), we have: - \( \omega^4 = \omega \) - \( \omega^5 = \omega^2 \) Thus, we can rewrite the determinant as: \[ \Delta = \begin{vmatrix} 1 & \omega^2 & 1 - \omega \\ \omega & 1 & 1 + \omega^2 \\ 1 & \omega & \omega^2 \end{vmatrix} \] ### Step 2: Expanding the Determinant We can expand this determinant using the first row: \[ \Delta = 1 \cdot \begin{vmatrix} 1 & 1 + \omega^2 \\ \omega & \omega^2 \end{vmatrix} - \omega^2 \cdot \begin{vmatrix} \omega & 1 + \omega^2 \\ 1 & \omega^2 \end{vmatrix} + (1 - \omega) \cdot \begin{vmatrix} \omega & 1 \\ 1 & \omega \end{vmatrix} \] ### Step 3: Calculating the 2x2 Determinants Now we compute each of the 2x2 determinants: 1. **First determinant:** \[ \begin{vmatrix} 1 & 1 + \omega^2 \\ \omega & \omega^2 \end{vmatrix} = 1 \cdot \omega^2 - \omega(1 + \omega^2) = \omega^2 - \omega - \omega^3 = \omega^2 - \omega - 1 \] 2. **Second determinant:** \[ \begin{vmatrix} \omega & 1 + \omega^2 \\ 1 & \omega^2 \end{vmatrix} = \omega \cdot \omega^2 - 1(1 + \omega^2) = \omega^3 - (1 + \omega^2) = 1 - 1 - \omega^2 = -\omega^2 \] 3. **Third determinant:** \[ \begin{vmatrix} \omega & 1 \\ 1 & \omega \end{vmatrix} = \omega^2 - 1 \] ### Step 4: Substituting Back Now substituting back into the expression for \( \Delta \): \[ \Delta = 1(\omega^2 - \omega - 1) - \omega^2(-\omega^2) + (1 - \omega)(\omega^2 - 1) \] ### Step 5: Simplifying \( \Delta \) Now simplifying \( \Delta \): 1. The first term: \[ \omega^2 - \omega - 1 \] 2. The second term: \[ + \omega^4 = \omega \] 3. The third term: \[ (1 - \omega)(\omega^2 - 1) = (1 - \omega)(\omega^2 - 1) = \omega^2 - \omega^3 - \omega + \omega^2 = 2\omega^2 - \omega - 1 \] Combining all these gives us: \[ \Delta = \omega^2 - \omega - 1 + \omega + 2\omega^2 - \omega - 1 = 3\omega^2 - 2 \] ### Step 6: Finding the Real Part Now we need to find \( |Re(\Delta)| \). The real part of \( \omega \) is \( -\frac{1}{2} \) and the real part of \( \omega^2 \) is also \( -\frac{1}{2} \). So, \[ Re(\Delta) = 3 \left(-\frac{1}{2}\right) - 2 = -\frac{3}{2} - 2 = -\frac{3}{2} - \frac{4}{2} = -\frac{7}{2} \] Thus, \[ |Re(\Delta)| = \frac{7}{2} \] ### Final Answer The final answer is: \[ |Re(\Delta)| = \frac{7}{2} \]
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