Non-editable png screen shot:

This is a try inserting a PDF of Korteweg–de Vries

This is the equation in MS Word:

danEquation_test

more

This is using the CodeCogs online equation editor:

\frac{\partial u}{\partial t}=6u\frac{\partial u}{\partial x}-\frac{\partial^3u}{\partial x^3}

OK, and now, Jetpack’s LaTeX plugin

This is the latex code generated from Apple’s Grapher. Grapher is located in /Applications/Utilities/Grapher.app