The PreTeXt Guide

Generally, you cannot add additional packages for use within mathematics. The exception is a package with support available optionally within MathJax. And it must have the same name as its normal LaTeX version. Then set a docinfo/latex-preamble/package element to be the common name of the package. (The cancel package is one such example.)

Then the supported macros of the package will be available with your mathematics elements, and you can use them within other macro definitions. We do not guarantee the absence of conflicts with other packages in use, even if employed by PreTeXt. Nor do we support debugging such conflicts.