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equation — A displayed mathematical equation
equation ::= (blockinfo?, (title,titleabbrev?)?, (informalequation| (alt?, (graphic+|mediaobject+|mathphrase+))))
| 
                         Name  | 
                     
                         Type  | 
                     
                         Default  | 
                  
| floatstyle | CDATA | None | 
| label | CDATA | None | 
An Equation is a formal mathematical equation
               (with an optional rather than required title).
               
            
If the MathML Module is used, Equation can
               also contain the mml:math element.
            
                  Formatted as a displayed block. For an inline equation, use InlineEquation.
                  
               
Processing systems that number equations or build a table of
                  equations at the beginning of a document may have difficulty correctly
                  formatting documents that contain both Equations
                  with Titles and Equations
                  without Titles.  You are advised to use
                  InformalEquation for equations without titles.
                  
               
In some future version of DocBook, probably
                  V5.0, even though the change has not yet been
                  announced, the Title on Equation
                  will be required.  For equations without titles, use
                  InformalEquation.
                  
               
These elements contain equation:
                  answer, appendix, article, bibliodiv, bibliography, blockquote, callout, caution, chapter, constraintdef, glossary, glossdef, glossdiv, important, index, listitem, msgexplan, msgtext, note, para, partintro, preface, procedure, qandadiv, qandaset, question, refsect1, refsect2, refsect3, refsection, refsynopsisdiv, revdescription, sect1, sect2, sect3, sect4, sect5, section, setindex, sidebar, simplesect, step, taskprerequisites, taskrelated, tasksummary, tip, warning.
               
The following elements occur in equation:
                  alt, blockinfo, graphic, informalequation, mathphrase, mediaobject, title, titleabbrev.
               
                        Label specifies an identifying string for presentation purposes.
                        
                     
                        Generally, an explicit Label attribute is
                        used only if the processing system is incapable of generating the label
                        automatically. If present, the Label 
                        is normative; it will used even
                        if the processing system is capable of automatic labelling.
                        
                     
example, figure, informalequation, informalexample, informalfigure, informaltable, inlineequation, subscript, superscript, table.
               
            
<!DOCTYPE equation PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
          "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd">
<equation><title>Fermat's Last Theorem</title>
  <alt>x^n + y^n ≠ z^n ∀ n > 2</alt>
  <graphic fileref="figures/fermat.png"/>
</equation>Alternatively, for relatively simple equations such as Fermat's Last
               Theorem, mathphrase is often sufficient:
            
<!DOCTYPE equation PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
          "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
<equation><title>Fermat's Last Theorem</title>
  <alt>x^n + y^n ≠ z^n ∀ n > 2</alt>
  <mathphrase>x<superscript>n</superscript>
+ y<superscript>n</superscript>
≠ z<superscript>n</superscript>
∀ n ≠ 2</mathphrase>
</equation>