Quadratic Gaussian period in the eleventh cyclotomic field
= Quadratic Gaussian period in the eleventh cyclotomic field
{c}
{title2=$\eta=\zeta_{11}+\zeta_{11}^3+\zeta_{11}^4+\zeta_{11}^5+\zeta_{11}^9$}
The unique quadratic subfield of $\mathbb Q(\zeta_{11})$ is
$$
\mathbb Q(\eta)=\mathbb Q(\sqrt{-11}),
\qquad
\eta=\frac{-1+\sqrt{-11}}2.
$$