Using fractions or expressions with sub- and superscripts may lead to uneven vertical spacing in math environments spanning several lines (i.e., align, gather, multline,...). A fix for align was presented here. Is there a similar solution for multline and/or gather?
This MWE illustrates the problem. The spacing after the first line is larger than after the second due to the sum + subscripts.
\documentclass{scrartcl}
\usepackage{amsmath}
\begin{document}
\begin{minipage}[bt]{0.35\linewidth}
\begin{multline*}
x=\sum_{i=1}^nx_n\\
+y_1+y_2+z_3\\
+z_1+z_2+z_3
\end{multline*}
\end{minipage}
\end{document}
\textstyle\sum\limits_{}^{}to get a better size for the sum sign. But this is my preference. – Sigur Apr 24 '15 at 16:55\setlength\jot{1.5ex}orspreadlinesfrommathtools– David Carlisle Apr 24 '15 at 20:56