Complex Numbers
Algebra of Complex Numbers
Grade Class 11

Question:

<p>If \(\alpha^{14}+\alpha^{10}+\alpha^6+\alpha^2+1=0\), then \(\alpha\) can be:</p>
e^(\pi i/8)
e^(\pi i/5)
e^(\pi i/7)
e^(\pi i/6)

Step-by-Step Solution

Key Concept: Factor: \alpha^1^4+\alpha^1^0+\alpha^6+\alpha^2+1 = \alpha^2(\alpha^1^2 + \alpha^8 + \alpha^4 + \alpha^0) + 1. This is related to cyclotomic polynomials. Dividing by \alpha^7: the equation becomes symmetric in nature.
<p>The equation $\sum_{k=0}^4 \alpha^{4k+2}=0$ is satisfied by 10th or 14th roots of unity. Testing $\alpha=e^{\pi i/7}=e^{2\pi i/14}$: this is a primitive 14th root, and by properties of cyclotomic polynomials, it satisfies the equation. ✓</p>
Correct Answer: C

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