5.2.1 Equation arrays

tbook treats a <math> element as an equation array, if it consists of only one <mtable>, with a groupalign attribute or one or more <mlabeledtr> rows. If you set groupalign="right center left", this leads to an eqnarray in LaTeX, and where `&' are in LaTeX, you have to use <maligngroup/> in MathML. Else the equations are just stacked and not aligned.

But as already mentioned, you can also use <m> inside <math>, which is very helpful for equation arrays.

If you use these elements within a MathML equation array, you can generate alignment markers (in LaTeX known as `&' signs) with `#' signs¹. Put them where they would be in LaTeX. Although MathML requires such a marker at the very beginning of an equation row, this is not true for LaTeX, and not true for tbook.

Here is an example:²

<math>
  <mtable groupalign="right center left">
    <mtr>
      <mtd id="test"> <m> 1+1 #=# 2 </m> </mtd>
      <mtd> <m> 4 #=# 2 &CenterDot; 2 </m> </mtd>
    </mtr>
  </mtable>
</math>

which is the same as LaTeX's

\begin{eqnarray}
  1+1 &=& 2 \label{Test} \\
  4   &=& 2 \cdot 2 \nonumber \\
\end{eqnarray}

and you don't want to see the HTML/MathML output tbook must create for that.

(By the way, being the only child element of an <mtd>, <m> is implicitly surrounded by an <mrow> which is necessary in this context.)