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I just wan't to align the equation like this example (Of course, I can't align these equations on the web page):

∵△ABC ≌ △A′B′C′
∴∠ABC = ∠A′B′C′
  ∠ACB = ∠A′C′B′
  ∠BAC = ∠B′A′C′

If I use &, these will be to much spaces...

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up vote 15 down vote accepted


You can use a space \, or use alignat as told by Gonzalo Medina

\usepackage{mathtools} %% provides amsmath with additional features and bug fixes
\usepackage{amssymb}   %% provides symbols like \because and \therefore

Using \verb|align|

    \because \triangle \mathrm{ABC}   &= \triangle \mathrm{A^{'}B^{'}C^{'}}   \\
    \therefore\, \angle \mathrm{ABC}  &= \angle  \mathrm{A^{'}B^{'}C^{'}}     \\
    \angle \mathrm{ACB}               &= \angle \mathrm{A^{'}C^{'}B^{'}}      \\
    \angle \mathrm{BAC}               &= \angle \mathrm{B^{'}A^{'}C^{'} }

Using \verb|alignat|
&\because   &\triangle \mathrm{ABC} &= \triangle \mathrm{A^{'}B^{'}C^{'}}   \\
&\therefore &\angle \mathrm{ABC}    &= \angle \mathrm{A^{'}B^{'}C^{'}}      \\
&           &\angle \mathrm{ACB}    &= \angle \mathrm{A^{'}C^{'}B^{'}}      \\
&           &\angle \mathrm{BAC}    &= \angle \mathrm{B^{'}A^{'}C^{'} }


enter image description here

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But I also need to ailgn \because and \therefore. – 比尔盖子 Sep 26 '12 at 1:50
@HarishKumar you're probably right in this case, but for other situations it's handy to know about alignat ;-) – Gonzalo Medina Sep 26 '12 at 2:09
@GonzaloMedina Agreed, my thoughts too. Hence added it in the answer. Thanks for reminding me. – Harish Kumar Sep 26 '12 at 2:28
Thanks. alignat is a great tool!! – 比尔盖子 Sep 26 '12 at 2:50
Another option will be to use falignat, which will force e therefore and because to the left of the display. – Aditya Sep 30 '12 at 13:06

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