Paper 2, Section II, H

Galois Theory | Part II, 2012

Let K,LK, L be subfields of C\mathbb{C} with KLK \subset L.

Suppose that KK is contained in R\mathbb{R} and L/KL / K is a finite Galois extension of odd degree. Prove that LL is also contained in R\mathbb{R}.

Give one concrete example of K,LK, L as above with KLK \neq L. Also give an example in which KK is contained in R\mathbb{R} and L/KL / K has odd degree, but is not Galois and LL is not contained in R\mathbb{R}.

[Standard facts on fields and their extensions can be quoted without proof, as long as they are clearly stated.]

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