Do you need to write formulae and heavy mathematical notation in your paper? Or maybe you need to write entire parts of your paper in LaTeX? Authorea's rich text editor is a true WYSIWYG editor (what you see is what you get), but it gives you the possibility to include mathematics as well as LaTeX and Markdown. If you have to type a simple (yet beautiful) equation such as
\(e^{i\pi}+1=0\), or a full fledged equation in LaTeX, such as eq.
\ref{eqn:lat} (below), you can! Read this tutorial:
How to add mathematical equations and formulae.