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Jun 21, 2013 at 2:49 comment added P Vanchinathan I meant, by higher degree expression, a polynomial of degree more than degree $\deg \alpha/2$, violating my expectation in the original question.
Jun 21, 2013 at 0:59 comment added Gerry Myerson If $\alpha$ is a root of unity, then $\alpha+\overline\alpha$ always has an expression as a polynomial in $\alpha$, since it's in the field you get by adjoining $\alpha$ to the reals. So I'm not sure I understand your comment.
Jun 21, 2013 at 0:48 vote accept P Vanchinathan
Jun 21, 2013 at 0:48 comment added P Vanchinathan Thanks. You have given a method to find examples. For a general root of unity $\alpha$ often it happens that the quadratic number $\alpha+\bar \alpha$ has a higher degree expression as a polynomial in \alpha$. I am trying to prove this having a sizeable number of examples.
Jun 20, 2013 at 2:34 history edited Gerry Myerson CC BY-SA 3.0
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Jun 20, 2013 at 2:06 history answered Gerry Myerson CC BY-SA 3.0