Merge pull request #70 from KaiGeffen/patch-2

typo

chapters/arithmetics-moonmath.tex

@@ -23,7 +23,7 @@ \subsection{Integers, natural numbers and rational numbers}
 \Z := \{\ldots, -3,-2,-1,0,1,2,3,\ldots\}
 \end{equation}
 
-If $a\in \Z$ is an integer, then we write $|a|$ for the \term{absolute value} of $a$, that is, the the non-negative value of $a$ without regard to its sign:
+If $a\in \Z$ is an integer, then we write $|a|$ for the \term{absolute value} of $a$, that is, the non-negative value of $a$ without regard to its sign:
 
 \begin{equation}
 |4|= 4