LaTex: Subequations with a left brace

A colleague in my lab wanted to use subequations (he wanted to number two equations with the same number but with .a and .b) while keeping a large left brace around the two equations.  I stumbled upon the way to do this using the package empheq.

To use the empheq package be sure to use the following line in your preamble.

\usepackage{empheq}

Then in your document you can use:

\begin{subequations}

\begin{empheq}[left=\empheqlbrace]{align}

    x &= y + z \\

     y &= \sin(\theta)

\end{empheq}

\end{subequations}