TeXmacs
![[Picture]](texmacs.gif)
File -> Export -> LaTeX:
\documentclass{article}
\begin{document}
Hello World! $\frac{\sqrt{a^2 + b^2}}{2}$
\end{document}
\begin{document}
Hello World! $\frac{\sqrt{a^2 + b^2}}{2}$
\end{document}