These are two useful LaTeX macros for creating equality-at and (the more general) relation-at signs. These macros depend on the mathtools package. As with all other macros you should add them to you preamble in order to use.

The general macro is the `\relat`

. It takes two arguments, the relation and an expression where the relation takes place (the “at”). The equality-at macro, `\eqat`

is a specific case of `\relat`

. I’ve created it because it is commonly used and only requires passing the “at” argument.

Here is the LaTeX code for the macros.

```
\newcommand{\relat}[2]{\mathrel{\bigg|_{\mathrlap{#2}}\mathrlap{#1}\hphantom{{}_{#2}}}}
\newcommand{\eqat}[1]{\mathrel{\bigg|_{\mathrlap{#1}}\mathrlap{=}\hphantom{{}_{#1}}}}
```

This is a basic example of how to use the macros. It should also give you an idea how they look.

```
documentclass{article}
\pagestyle{empty}
\usepackage{mathtools}
\newcommand{\relat}[2]{\mathrel{\bigg|_{\mathrlap{#2}}\mathrlap{#1}\hphantom{{}_{#2}}}}
\newcommand{\eqat}[1]{\mathrel{\bigg|_{\mathrlap{#1}}\mathrlap{=}\hphantom{{}_{#1}}}}
\begin{document}
\[
\Delta=\left[\begin{array}{cc} P & Q\\ f' & g'\end{array}\right]
\eqat{\Gamma}
\left[\begin{array}{cc} -2t & 4t\\ 1 & -2\end{array}\right]
\]
\[
\cos x \relat{\leq}{x=\frac{\pi}{3}} \frac{\sqrt{@}}{2}
\]
\end{document}
```