Revert "Modular arithmetic work actually irrelevant"

Realised I was wrong
This reverts commit 23826ea2.

main.tex

@@ -838,6 +838,28 @@ this happens when:
 	< \frac{1}{\lcm(m,2n^2)}
 \end{equation}
 
+\begin{sagesilent}
+rhs_numerator = (
+	positive_radius_condition
+	.rhs()
+	.subs([q_value_expr,beta_value_expr])
+	.factor()
+	.numerator()
+)
+\end{sagesilent}
+
+\noindent
+Considering the numerator of the right-hand-side:
+
+\begin{align}
+	\sage{rhs_numerator}
+	&\equiv (a(-a^{-1}b)+2b)a &\mod n
+\\
+	&\equiv ab &\mod n
+\end{align}
+
+And so, we also have $a(ar+2b) \equiv ab$ (mod $\lcm(m,2n^2)$).
+
 \minorheading{Irrational $\beta$}