Title: Formatting subequations where one of them is a piece-wise function
Tags: horizontal-alignment;subequations
Question: I have the following LaTeX code:

```\begin{subequations} 
\begin{align}
F_h(t) = F(\Delta y) = \left\{
            \begin{array}{lr}
                K_h (\Delta y)^{P_h} \; \text{if} \; \Delta y &gt; 0\\
                0 \; \; \hspace{1.23cm}\; \text{if} \; \Delta y \leq 0
            \end{array}
            \right. \label{eqn: hammer1}\\
F_h(t) = -m_h \label{eqn: hammer2}
\end{align}
\end{subequations}
```

when I compile it, the 2nd equation is aligned to the right-most margin of equation 1.
How do I set it such that the 2nd equation is aligned to the left-most margin of the first equation?


Here is the accepted answer: You forgot to place the alignment character inside your ```align``` construction. Also, consider using ```cases``` for the conditional constructions:



```\documentclass{article}
\usepackage{mathtools}% http://ctan.org/pkg/mathtools

\begin{document}

\begin{subequations} 
\begin{align}
F_h(t) &amp;= F(\Delta y) = {\begin{cases}
                K_h (\Delta y)^{P_h} &amp; \text{if $\Delta y &gt; 0$} \\
                0                    &amp; \text{if $\Delta y \leq 0$}
            \end{cases}}
            \label{eqn: hammer1} \\
F_h(t) &amp;= -m_h \label{eqn: hammer2}
\end{align}
\end{subequations}

\end{document}
```



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