Use mathsf for entire block/environment

Question

Basically, I want to definite a flalign environment where all the math uses mathsf by default.

I can't just wrap the whole thing in a mathsf command because there might be line breaks and & separators that break things.

Is there a version of mathsf that works like \color where it sets the font style for the entire block, instead of just for the argument?

Answer 1

You can use sansmath, supplementing it with a sans serif font for large operators.

\documentclass{article}
\usepackage{amsmath}
\usepackage{sansmath}

\SetSymbolFont{largesymbols}{sans}{OMX}{iwona}{m}{n}

\begin{document}

\sansmath

\begin{flalign}
A&=B & C&=D & u&=v \\
x&=\sum_{i=1}^n a_i & y&=M\otimes N & z&=U^v & x\ne z
\end{flalign}

\unsansmath

\begin{flalign}
A&=B & C&=D & u&=v \\
x&=\sum_{i=1}^n a_i & y&=M\otimes N & z&=U^v & x\ne z
\end{flalign}

\end{document}