Equations

One advantage of L^ATEX is that it can automatically number equations and refer to these equation numbers in text. While plain TEX's method of equation numbering (explicit numbering using \leqno) works in the SIAM macro, it is not preferred except in certain cases. SIAM style guidelines call for aligned equations in many circumstances, and L^ATEX's {eqnarray} environment is not compatible with \leqno and L^ATEX is not compatible with the plain TEX command \eqalign and \leqalignno. Since SIAM may have to alter or make aligned certain groups of equations, it is necessary to use the L^ATEX system of automatic numbering.

Sometimes it is desirable to designate subequations of a larger equation number. The subequations are designated with (roman font) letters appended after the number. SIAM has supplemented its macros with the subeqn.sty style which defines the environment {subequations}.

\begin{subequations}
\begin{equation}
 y_k =  B  y_{k-1} +  f, \qquad k=1,2,3,\ldots  \label{EXk}
\end{equation}
for  any initial vector $ y_0$.   Then 
\begin{equation}
 y_k\rightarrow  u \mbox{\quad iff\quad} \rho( B)<1.
\end{equation}
\end{subequations}

All equations within the {subequations} environment will keep the same overall number, but the letter designation will increase.