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**1327**on Tue Nov 05, 2013 7:11 pm

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## multiple alignment points and \split environmentAdd tags
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## multiple alignment points and \split environmentHi there,
I'd like to display a two line equation aligned in more than one place across two lines, but only supply it with one number. I.e. in an equation like: a=b=c ab=bc=c^2 I'd like the = signs to be aligned vertically, and I want 1 equation number to the right halfway between the two lines. I know alignment can be done with \alignat, and the numbering can be done with \split, but I can't seem to get both things at once. MWE: - Code: Select all • Open in writeLaTeX
`\documentclass[10pt,a4paper]{article}` \usepackage{amsmath} \begin{document} \section{Test} \begin{alignat}{3} a&={}&b&={}&c\\ ab&={}&bc&={}&c^2 \end{alignat} \begin{alignat}{3} a&=b&=c\\ ab&=bc&=c^2 \end{alignat} \begin{equation} \begin{split} a&=b=c\\ ab&=bc=c^2 \end{split} \end{equation} \end{document}
Also, alignat seems to require an extra {}& per equal sign that I don't quite understand (top equation in the MWE, since the one below has strange spacing). Could someone explain this to me? Furthermore, the split environment will produce error messages if I put more & symbols on one line. For example, inserting this in the MWE will produce error messages: - Code: Select all • Open in writeLaTeX
`\begin{equation}` \begin{split} a&=b&=c\\ ab&=bc&=c^2 \end{split} \end{equation}
Could someone help me align and number things the way I like? Thanks in advance. (Some more details I'm not quite sure are useful: I use WinEdt 6.0 with MikTex 2.8 and PDFTexify) Last edited by Drugbird on Thu Sep 2nd, 2010, edited 1 time in total.
- Drugbird
**Posts:**2**Joined:**Tue Aug 31st, 2010
## Re: multiple alignment points and \split environmentIt has to look a bit different. The code below shows only the relevant part.
- Code: Select all • Open in writeLaTeX
`\begin{equation}` \begin{alignedat}{2} a &= b & &= c\\ ab &= bc & &= c^2 \end{alignedat} \end{equation}
See the amsmath manual for details. More stuff about math typesetting can be found in the »Math mode« document. Best regards and welcome to the board Thorsten LaTeX Community Moderator
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localghost - Site Moderator
**Posts:**9219**Joined:**Fri Feb 2nd, 2007**Location:**Braunschweig, Germany
## Re: multiple alignment points and \split environmentThanks a lot, localghost. This is exactly what I was looking for.
I'm still not quite sure though why you need three & symbols per line. My reasoning is that there are only two equal signs that need to be aligned, so you'd also need two & symbols. I tried searching the amsmath documentation, but was unable to find it... Any help? - Drugbird
**Posts:**2**Joined:**Tue Aug 31st, 2010
## Re: multiple alignment points and \split environment
Consider the alignat environment as an array with special alignment of the columns. - Code: Select all • Open in writeLaTeX
`\begin{array}{@{}r@{\,=\,}lr@{\,=\,}l@{}}` a & b & c \\ aa & bb & cc \end{array}
If you declare an alignat environment with n as its mandatory argument for the number of equal signs to be aligned, you will need n+1 alignment characters (ampersands) to get the right alignment. Take a look at Sections 3.6 and 3.7 of the amsmath manual. You can find similar descriptions in the »Math mode« document. LaTeX Community Moderator
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localghost - Site Moderator
**Posts:**9219**Joined:**Fri Feb 2nd, 2007**Location:**Braunschweig, Germany
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