# Aligning equations while using cases in align environment

I have the following code:

\begin{align}
& a+b+c+d+e+f = 15000 & \text{for } a = 1 ... 15  \\
& D_t=
\begin{cases}
\text{equation} , & \text{for } t = 1 ... 10 \\
\text{another equation} , & \text{for } t = 1 ... 10 \\
\end{cases}
\end{align}


This produces the following:

However, I would like the "for" arguments in cases to be aligned to those in the align environment, which would look something like:

I was wondering if there is a way of doing this automatically, rather than using manual spacing. I have tried using arrays, however it didn't seem to solve the issue.

Thank you.

• The best choice may depend on whether equation and another equation are of single-line height, or whether they are tall (include display fractions for example). – Steven B. Segletes Apr 20 '18 at 14:31
• In my case, both equations are of single-line height. – Story Maths Apr 20 '18 at 14:37

The \Centerstack retains a settable but fixed baselineskip. Thus, using \Centerstacks to set both the equations of the case, as well as (separately) the conditions of the case, will insure that their baselineskips are compatible.

\documentclass{report}
\usepackage{amsmath}
\usepackage[usestackEOL]{stackengine}
\stackMath
\setstackgap{L}{1.2\normalbaselineskip}
\begin{document}
\begin{align}
& a+b+c+d+e+f = 15000 && \text{for } a = 1 ... 15  \\
& D_t= \left\{\Centerstack[l]{\text{equation} ,\\ \text{another equation}}\right.&&
\Centerstack{ \text{for } t = 1 ... 10 \\ \text{for } t = 1 ... 10}
\end{align}
\end{document}


Here are two ways to obtain it:

\documentclass{article}
\usepackage{mathtools}

\begin{document}

\begin{alignat}{2}
& a+b+c+d+e+f = 15000 &\quad & \text{for } a = 1 ... 15 \\
& D_t=
\begin{cases}
\text{equation} , \\
\text{another equation} ,
\end{cases} & & \begin{aligned}
\text{for } t = 1 ... 10 \\\text{for } t = 1 ... 10
\end{aligned}
\end{alignat}

\begin{alignat}{2}
& a+b+c+d+e+f = 15000 &\quad & \text{for } a = 1 ... 15 \\
& D_t=
\mathrlap{\begin{cases}
\text{equation} , & \text{for } t = 1 ... 10 \\
\text{another equation} ,\hspace{1.9em}& \text{for }t = 1 ... 10
\end{cases}}
\end{alignat}

\end{document}


This can be easy if we force the left part of each equation to occupy a fixed width, using for example \makebox[20em][l]{..}.

\documentclass{report}
\usepackage{amsmath}
\begin{document}

\begin{align}
&\makebox[20em][l]{$a+b+c+d+e+f = 15000$} \text{for } a = 1 \dots 15 \\
&\makebox[20em][l]{$D_t=\begin{cases} \text{equation}, \\ \text{another equation}, \end{cases}$} \begin{aligned}\text{for } t = 1 \dots 10\\
\text{for } t = 1 \dots 10\end{aligned}
\end{align}

\end{document}