mjo-algebra: add the \ideal{} generated by a set.

[mjotex.git] / examples.tex

diff --git a/examples.tex b/examples.tex
index 9e376ccd58757500d96fbf6df2f5395e70b6c39b..af125a726265dbfd53b150bc42cca2cfeb5c3c6f 100644 (file)
--- a/examples.tex
+++ b/examples.tex
@@ -29,7 +29,9 @@
     If $R$ is a \index{commutative ring}, then $\polyring{R}{X,Y,Z}$
     is a multivariate polynomial ring with indeterminates $X$, $Y$,
     and $Z$, and coefficients in $R$. If $R$ is a moreover an integral
-    domain, then its fraction field is $\Frac{R}$.
+    domain, then its fraction field is $\Frac{R}$. If $x,y,z \in R$,
+    then $\ideal{\set{x,y,z}}$ is the ideal generated by $\set{x,y,z}$,
+    which is defined to be the smallest ideal in $R$ containing that set.
   \end{section}
 
   \begin{section}{Algorithm}
@@ -68,9 +70,31 @@
   \begin{section}{Common}
     The function $f$ applied to $x$ is $f\of{x}$. We can group terms
     like $a + \qty{b - c}$ or $a + \qty{b - \sqty{c - d}}$. Here's a
-    set $\set{1,2,3} = \setc{n \in \Nn[1]}{ n \le 3 }$. Here's a pair
-    of things $\pair{1}{2}$ or a triple of them $\triple{1}{2}{3}$,
-    and the factorial of the number $10$ is $\factorial{10}$.
+    set $\set{1,2,3} = \setc{n \in \Nn[1]}{ n \le 3 }$. The tuples go
+    up to seven, for now:
+    %
+    \begin{itemize}
+      \begin{item}
+        Pair: $\pair{1}{2}$,
+      \end{item}
+      \begin{item}
+        Triple: $\triple{1}{2}{3}$,
+      \end{item}
+      \begin{item}
+        Quadruple: $\quadruple{1}{2}{3}{4}$,
+      \end{item}
+      \begin{item}
+        Qintuple: $\quintuple{1}{2}{3}{4}{5}$,
+      \end{item}
+      \begin{item}
+        Sextuple: $\sextuple{1}{2}{3}{4}{5}{6}$,
+      \end{item}
+      \begin{item}
+        Septuple: $\septuple{1}{2}{3}{4}{5}{6}{7}$.
+      \end{item}
+    \end{itemize}
+    %
+    The factorial of the number $10$ is $\factorial{10}$.
 
     The Cartesian product of two sets $A$ and $B$ is
     $\cartprod{A}{B}$; if we take the product with $C$ as well, then