added index "proof of induction"

git-svn-id: svn://svn.code.sf.net/p/rodin-b-sharp/svn/trunk/Handbook@15313 1434b563-b632-4741-aa49-43a3a8374d2e

org.rodinp.handbook.feature/latex/faq.tex

@@ -295,7 +295,7 @@ This can take some time. A ``Progress'' view can be opened at the bottom right o
 Yes, it is.  Check out Section~\ref{use_provers_effectively} to begin using the provers.
 
 \subsection{How can I do a Proof by Induction?}
-
+\index{induction@proof by induction}
 \href{http://wiki.event-b.org/index.php/Induction_proof}{This page about proof by induction} will give you some starting tips.
 
 \subsection{What do the labels on the proof tree mean?}