# Vertical space before and after equations

The vertical space before and after equation (1) is greater than the vertical space before and after equation (2).

Which is the rule/reason for that?

\documentclass{book}
\usepackage{amsmath,amsfonts}
\usepackage{setspace}
\usepackage{mwe}
\begin{document}
\doublespacing
Is it normal that the vertical space before and after this equation:
$$a = b + c$$
is more than the space before and after this other equation?
$$d=\sum_{i=1}^{k}e_i$$
\blindtext
\end{document}


• Yes, it is normal. Measure the distance between the baselines. – egreg Aug 14 '19 at 22:00
• The spaces are exactly the same -- compare the gaps between the surrounding text, not the distance from the highest/lowest elements of the displayed material. The difference you observe is the fact that there is a large operator with limits in the second display; that is not part of the defined measurement, which is correctly described by @egreg. – barbara beeton Aug 14 '19 at 22:22
• @egreg Thank you! Would you like to add an answer? – CarLaTeX Aug 15 '19 at 4:44
• @barbarabeeton idem ^^^ – CarLaTeX Aug 15 '19 at 4:45