Improve description of smallmatrix

I did not notice there was already something about it.

lib/doc/Math.lyx

@@ -228,6 +228,7 @@ subequations
 \html_css_as_file 0
 \html_be_strict false
 \author -563046850 "Jean-Marc LASGOUTTES"
+\author 47243155 "Jean-Marc"
 \end_header
 
 \begin_body
@@ -284,7 +285,13 @@ author: Uwe Stöhr
 
 
 \family sans
-Version 2.3.x
+Version 2.
+\change_inserted 47243155 1563226038
+4
+\change_deleted 47243155 1563226038
+3
+\change_unchanged
+.x
 \end_layout
 
 \begin_layout Standard
@@ -4804,6 +4811,8 @@ arg   "newline-insert newline"
 \begin_inset VSpace bigskip
 \end_inset
 
+
+\change_deleted 47243155 1563226130
 The 
 \change_deleted -563046850 1563190969
 
@@ -5369,7 +5378,13 @@ arraystretch
 \end_layout
 
 \begin_layout Standard
-To set matrices into a text line, the command 
+
+\change_inserted 47243155 1563226178
+Small inline matrices can also be obtained using 
+\change_deleted 47243155 1563226182
+To set matrices into a text line,
+\change_unchanged
+ the command 
 \series bold
 
 \backslash
@@ -5387,7 +5402,11 @@ smallmatrix
 
 \end_inset
 
- is used.
+
+\change_deleted 47243155 1563226186
+ is used
+\change_unchanged
+.
  When it is inserted a blue box with two dashed lines appears.
  In this box the matrix is inserted.
 \end_layout
@@ -5399,7 +5418,11 @@ C & D
 \end{smallmatrix}\right)$
 \end_inset
 
- in a text line.
+ in a text line
+\change_inserted 47243155 1563226243
+ with automatic delimiters around it
+\change_unchanged
+.
 \end_layout
 
 \begin_layout Section