Created the Abstract Algebra theorems and definitions cheat sheet

part-5/chapters/chapter-33/the-constructible-regular-n-gons.tex

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+\section{The Constructible Regular $\mathbf{n}$-gons}
+
+\begin{lemma}
+	Let $n$ be a positive integer and let $\omega = \cos(2\pi/n)+i\sin(2\pi/n)$. Then $\Q(\cos(2\pi/n)) \subseteq \Q(\omega)$.
+\end{lemma}
+
+\begin{theorem}[(Gauss, 1796)]
+	It is possible to construct the regular $n$-gon with a straightedge and compass if and only if $n$ has the form $2^kp_1p_2\dots p_t$, where $k \geq 0$ and the $p_i$'s are distinct primes of the form $2^m + 1$.
+\end{theorem}