Math & Science ⇒ Removing whitespace in align*

[Singularity]

Hi all. I can't get the extra whitespace in an align* to disappear. Any suggestions?

Code: Select all

\documentclass[12pt,fleqn,reqno]{article}
\begin{document}
\begin{align*}
	\ddot{u}_1 &= k(u_{0} &-2u_{1} &+u_{2})  \\
	\ddot{u}_2 &= k(u_{1} & -2u_{2} &+u_{3}) \\
	\vdots & & &\\
	\ddot{u}_{_N} &= k(u_{_{N-1}} &-2u_{_N} &+u_{_{N+1}})
.\end{align*}
\end{document}

For whatever reason, the second ampersand (&) in each line wants to push the whole rest of the line to the center of the page. I tried adding ampersands to the beginning of each line, and tried adding an extra one at the end of each line (as in some examples I've seen), but to no avail.

I also tried removing 'fleqn,reqno' parms at the top.

[Stefan Kottwitz]

You could use an alignat environment. In this modified example, all required points are aligned without too much space:

Code: Select all

\documentclass[12pt,fleqn,reqno]{article}
\usepackage{amsmath}
\begin{document}
\begin{alignat*}{4}
   \ddot{u}_1 &= k(u_{0} &&-2u_{1} &&+u_{2})  \\
   \ddot{u}_2 &= k(u_{1} && -2u_{2} &&+u_{3}) \\
   \vdots & & &\\
   \ddot{u}_{_N} &= k(u_{_{N-1}} &&-2u_{_N} &&+u_{_{N+1}})
\end{alignat*}
\end{document}

Stefan

[Singularity]

Well, that worked the way I wanted, but now I decide I don't like the way that looks. I've decided to just remove all the extra ampersands (except before the equal sign), and display it the way everybody else probably does.

Thanks for the alignat tip.