Can I make a line in a multi-line math block have a minimum line height?
For example,
\begin{align*}
x &= 1 \\
y &= 2
\end{align*}
renders as
but I want the second line to have more space "reserved", kind of like this (I've drawn in a red spacer bar to visualize):
\jot will helps you:
\documentclass{book}
\usepackage{mathtools}
\usepackage{lipsum}
\setlength{\jot}{24pt}
\begin{document}
\lipsum
\begin{align}
a+b=c\\
x=y=z
\end{align}
\end{document}
\jot -- so please definitely leave your answer up.
\jot isn't a mathtools thing, it's from amsmath. But mathtools dies provide the env spreadlines to change jot locally. Just mentioning since some users cannot distinguish the two packages and complains that mathtools has a problem when the problem is in ansmath
\ruleUse a zero-width \rule as a "strut" at the start of the second line:
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{align*}
x &= 1 \\
\rule[-1.3\baselineskip]{0pt}{3\baselineskip} y &= 2
\end{align*}
\end{document}
It looks like this:
The syntax of \rule is \rule[raise]{width}{height}.
The way I arrived at the -1.3\baselineskip and 3\baselineskip values is by checking the definition for a \strut, which is \rule[-0.3\baselineskip]{0pt}{\baselineskip}, and subtracting 1\baselineskip from the raise and adding twice that to the height.
We can visualize the effect of the rule by temporarily setting its width to 1pt:
![x = 1, new line, [a vertical bar taking up vertical space] y = 2](https://cdn.statically.io/img/i.sstatic.net/fReaC06t.png)
\vphantomIf instead of setting a height value, you want to reserve the amount of space that some specific formula would take, you can use \vphantom instead of \rule. The \vphantom macro creates a zero-width box with as much height as its contents.
For example, this code reserves as much space as a summation sign would take:
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{align*}
x &= 1 \\
\vphantom{\sum_0^x} y &= 2
\end{align*}
\end{document}
\documentclass and all packages used.