You can insert equations into topics using the MathFlow equation editor, which is fully integrated into Codex. In order to use MathFlow, you must purchase a license from Design Science. To learn more about MathFlow, or to request a free trial, contact Design Science.
When you insert an equation into a topic, Codex creates an image file for the equation and saves the equation as MathML directly within the topic. Whenever you edit the equation, Codex updates the image and MathML.