Math & Science ⇒ Gathered Alignment of Terms in Equation

[niles]

Hi

I have the following MWE doing what it is supposed to do:

Code: Select all

\documentclass[a4paper]{article}
\usepackage[ansinew]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{amsmath, amsthm, amssymb}

\begin{document}
\begin{equation}
  \begin{aligned}
		\alpha = \beta &+ \gamma \\ %gamma and delta are supposed to be above eachother
		               &- \delta
   \end{aligned}
\end{equation}
\end{document}  

Howver now I want to add a new line and thus a new equality sign =, and this I want to be below the one after \alpha. I tried using

Code: Select all

\documentclass[a4paper]{article}
\usepackage[ansinew]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{amsmath, amsthm, amssymb}

\begin{document}
\begin{equation}
  \begin{aligned}
		\alpha &= \beta &+ \gamma \\ %gamma and delta are supposed to be above eachother
		       &        &- \delta \\
                       &= \Pi 
   \end{aligned}
\end{equation}
\end{document} 

but the result does not look correct. I guess I'm using the ampersands wrong, but do I need to insert some "whitespace" in order to deal with two &'s per row?

Thanks in advance.

Best,
Niles.

[cgnieder]

You need to double the ampersands:

Code: Select all

\documentclass[a4paper]{article}
\usepackage[ansinew]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{amsmath, amsthm, amssymb}

\begin{document}

\begin{equation}
  \begin{aligned}
    \alpha &= \beta &&+ \gamma \\ %gamma and delta are supposed to be above each other
           &        &&- \delta \\
           &= \Pi
  \end{aligned}
\end{equation}

\end{document}

Alignment in math environments typically is alternating right and left

Code: Select all

\begin{aligned}
  right & left    &    right & left \\
  right & left    &    right & left
\end{aligned}

Regards

[niles]

Hi

Thanks for the reply. I tried it out, but the terms on the right part (for the two first rows) are pushed to the right. Is there a way to correct this?

[cgnieder]

Maybe something like this?

Code: Select all

\documentclass[a4paper]{article}
% \usepackage[ansinew]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{amsmath, amsthm, amssymb}

\newcommand*\phantomrel[1]{\mathrel{\phantom{#1}}}
\newcommand*\mllap[1]{\llap{$#1$}}

\begin{document}

\begin{equation}
  \begin{aligned}
    \alpha &= \phantom{\Pi}\mllap{\beta} + \gamma \\ %gamma and delta are supposed to be above eachother
           &\phantomrel{=} \phantom{\Pi} - \delta \\
           &= \Pi
  \end{aligned}
\end{equation}

\end{document}

Regards

[niles]

Thanks, it works. But I am a little surprised that LaTeX doesn't offer a more "automated" approach.

Best wisshes,
Niles.

[cgnieder]

Even better (and easier):

Code: Select all

\documentclass[a4paper]{article}
% \usepackage[ansinew]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{amsmath, amsthm, amssymb}

\newcommand*\phantomrel[1]{\mathrel{\phantom{#1}}}

\begin{document}

\begin{equation}
  \begin{aligned}
    \alpha &= \beta + \gamma \\ %gamma and delta are supposed to be above eachother
           &\phantomrel{=} \phantom{\beta} - \delta \\
           &= \Pi
  \end{aligned}
\end{equation}

\end{document}

Regards