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Old 2020-03-03, 21:36   #3
wildrabbitt
 
Jul 2014

3·149 Posts
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The book I'm reading says that given a qth root of unity \[\zeta\], every polyonomial in \[\zeta\] can be expressed as


\[A_1\zeta^1 + A_2\zeta^2 + A_3\zeta^3 +A_4\zeta^4...A_{q-1} + \zeta^{q-1}\]


and the expression is unique because the cyclotomic polynomial of degree q-1 of which \[\zeta\] is a zero is irreducible over the rational field so \[\zeta\] can't be a root of a polynomial of lower degree with integral coefficients.


I know the proof that cyclotomic polynomials are irreducible but I don't get why..... (don't even know what I'm unclear about).


I'm lost. I asked the question I asked orignally because I thought it might help me understand.

Last fiddled with by wildrabbitt on 2020-03-03 at 21:39
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