3

I have two little problems with the alignment here:

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

\begin{alignat*}{6}
\Phi \left(\sum\limits_{m\in M}r_m\delta _m + \sum\limits_{m\in M}r_m'\delta _m\right) &= \Phi \Bigg( &&\sum\limits_{m\in M}r_m\delta _m + r_m'\delta _ m\Bigg)\\
&= &&\sum\limits_{m\in M}(r_m+r_m')\phi (m)\\
&= &&\sum\limits_{m\in M}r_m\phi (m) &+ & &\sum\limits_{m\in M}r_m'\phi (m)\\
&=\Phi \Bigg(&&\sum\limits_{m\in M}r_m\delta _m\Bigg) &+ & \Phi \Bigg(&\sum\limits_{m\in M}r_m'\delta _m\Bigg)
\end{alignat*}
\end{document}

Firstly, the second sigmas in the last two lines don't seem to be aligned.

Second, is there a way to remove that space between those the two plus signs and the terms before them (on the last two lines)?

Thanks!

2
  • Why alignat with so many alignment points? It's perfectly OK to do \documentclass{article} \usepackage{amsmath} \begin{document} \begin{align*} \Phi \Bigl(\sum\limits_{m\in M}r_m\delta _m + \sum\limits_{m\in M}r_m'\delta _m\Bigr) &= \Phi \Bigl( \sum\limits_{m\in M}r_m\delta _m + r_m'\delta _ m\Bigr)\\ &= \sum\limits_{m\in M}(r_m+r_m')\phi (m)\\ &= \sum\limits_{m\in M}r_m\phi (m) + \sum\limits_{m\in M}r_m'\phi (m)\\ &=\Phi \Bigl( \sum\limits_{m\in M}r_m\delta _m\Bigr) + \Phi \Bigl( \sum\limits_{m\in M}r_m'\delta _m\Bigr) \end{align*} \end{document} I also reduced the parenthesis size. Dec 15, 2014 at 0:52
  • My original plan was to align all the first sigmas and align all the second sigmas, but looking at it now, it looks better how you did it. Thanks! Dec 15, 2014 at 0:57

1 Answer 1

3

The following provides the alignment you're after:

enter image description here

\documentclass{article}
\usepackage{mathtools}% mathtools loads amsmath
\begin{document}

\begin{alignat*}{6}
  \Phi \Biggl(\sum_{m \in M} r_m \delta_m + \sum_{m \in M} r_m' \delta_m \Biggr)
    &= \Phi \Biggl( && \mathrlap{{}\sum_{m \in M} r_m \delta_m + r_m' \delta_m \Biggr)} \\
    &= && \mathrlap{{}\sum_{m \in M}\bigl(r_m + r_m'\bigr)\phi (m)} \\
    &= && \sum_{m \in M} r_m \phi (m) &&{}+{} &&\sum_{m \in M} r_m' \phi (m) \\
    &= \Phi \Biggl( && \sum_{m \in M} r_m \delta_m \Biggr) &&+ \Phi \Biggl(&& \sum_{m \in M} r_m' \delta_m \Biggr)
\end{alignat*}
\end{document}

I wouldn't align the second set of summations though.

1
  • Usually \bigg is used in these cases.
    – egreg
    Dec 15, 2014 at 8:46

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