The existing question Typeset WHOLE document in sans-serif, Including Math Mode uses the sansmath package to use helvet glyphs also in math-mode. But being not designed for use in math mode, the results don't look convincing.
According to this survey of free math fonts, it seems to be possible to use another font (mentioned are cmbright and lxfonts as similar) for math-mode in combination with helvet for text-mode. However, I cannot find pointers on how to setup the document appropriately. (How) can it be done?
The obligatory MWE:
\documentclass{article}
\usepackage{helvet} % for text-mode
\renewcommand{\familydefault}{\sfdefault}
% \usepackage{cmbright} % one of these for...
% \usepackage{lxfonts} % math-mode only
\usepackage[math]{blindtext}
\begin{document}
\blindmathpaper
\end{document}

