>>874

つづき
(Brent Everitt先生、これお薦めです。カラーの絵が豊富で分り易い。（練習問題の解答が無くなっているね（＾＾ ））
https://arxiv.org/abs/1804.04657
Galois Theory - a first course
Brent Everitt
(Submitted on 12 Apr 2018)
These notes are a self-contained introduction to Galois theory, designed for the student who has done a first course in abstract algebra.
https://arxiv.org/pdf/1804.04657.pdf

ここで、円分体そのものじゃないけど、
方程式x^5 ? 2＝0のガロア群の絵解きがあるんだ。殆どこれで尽くされているね
イントロの部分で、”0. What is Galois Theory?”の章があって、
P7 (0.8)
A pentagon has 10 geometric symmetries, and you can check that all arise as symmetries of
the roots of x^5 ? 2 using the same reasoning as in the previous example. But this reasoning also
gives a symmetry that moves the vertices of the pentagon according to:
図略
This is not a geometrical symmetry ? if it was, it would be pretty disastrous for the poor pentagon.
Later we will see that for p > 2 a prime number, the solutions to xp ?2 = 0 have p(p?1) symmetries.
(引用終り)
とある
これの詳しい記述が本文にある

(なお、下記こちらは、過去スレでも紹介した2007版で古いけど、内容はほぼ同じで、最後に練習問題の解答が付いているよ（＾＾ )
http://www-users.york.ac.uk/~bje1/galnotes.pdf
Symmetries of Equations: An Introduction
to Galois Theory
Brent Everitt, version 1.12, December 19, 2007.
Department of Mathematics, University of York, York
以上