bracketssubequations
I have two equations, places inside subequations. How can I put the bracket { on the left side of these subequations?
P.S.I tried cases, but it doesn't work there – error "Missing $ inserted"
\begin{subequations} \begin{cases}
\begin{equation} subeq.1 \end{equation}
\begin{equation} subeq.2 \end{equation}
\end{cases} \end{subequations}
I think that some information about the actual expressions might be useful to decide which structure(s) would be best to use; in its present form (using arrays for the two subgroups), one could use a cases environment for the outer brace:
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}
\begin{cases}
\left\{
\begin{array}{lcl}
1 \\
2
\end{array}
\right. \\
\left\{
\begin{array}{lcl}
3 \\
4
\end{array}
\right.
\end{cases}
\end{equation}
\end{document}
Here's another option, using a gather environment for the whole structure, and nested arrays:
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{gather}
\left\{
\begin{array}{@{}l@{}}
\left\{
\begin{array}{lcl}
1 \\
2
\end{array}
\right. \\
\left\{
\begin{array}{lcl}
3 \\
4
\end{array}
\right.
\end{array}
\right.
\end{gather}
\end{document}
By the way, your code has some typos like \end{array{lcl}.
I see no reasons for aligning the equals signs in the two equations, so I provide also a solution without such alignment.
The best trick, in my opinion, is to use split:
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{subequations}
\begin{align}
\begin{split}
Z^0(e^{j\omega h^0})
&= P^0_{11}(e^{j\omega h^0})\Lambda^0(e^{j\omega h^0}) \\
&\qquad+ P^0_{12}(e^{j\omega h^0})\mathcal{I}_{zoh}(e^{j\omega h^0})Q(e^{j\omega h})\\
&\qquad\times \frac{1}{F}\sum_{f=0}^{F-1}P^0_{12}
(e^{j\omega h^0-\frac{f}{F}\omega^0_s})\Lambda^0(e^{j\omega h^0-\frac{f}{F}\omega^0_s})
\end{split}
\intertext{where}
Q(\omega) &= (I-C(\omega)P_{22}(\omega))^{-1}C(\omega)
\end{align}
\end{subequations}
\begin{subequations}
\begin{equation}
\begin{split}
Z^0(e^{j\omega h^0})
&= P^0_{11}(e^{j\omega h^0})\Lambda^0(e^{j\omega h^0}) \\
&\qquad+ P^0_{12}(e^{j\omega h^0})\mathcal{I}_{zoh}(e^{j\omega h^0})Q(e^{j\omega h})\\
&\qquad\times \frac{1}{F}\sum_{f=0}^{F-1}P^0_{12}
(e^{j\omega h^0-\frac{f}{F}\omega^0_s})\Lambda^0(e^{j\omega h^0-\frac{f}{F}\omega^0_s})
\end{split}
\end{equation}
where
\begin{equation}
Q(\omega) = (I-C(\omega)P_{22}(\omega))^{-1}C(\omega)
\end{equation}
\end{subequations}
\end{document}
Best Answer
stealing @Bernard's example, i've expanded it to show a multi-line situation. the
[t]is a necessary option on thealignedblock to keep the block from being centered vertically, but unfortunately it also has the effect of placing the equation number on the top line of that component.one other comment ... bernard's answer uses "unicode" superscripts. doesn't always work (and there aren't unicode superscripts for greek letters or really anything but digits), so it's not recommended to use those in math.
but otherwise, bernard's answer is solid.