Most technical writers grapple with complex equation creation/updating and resort to purchasing a MathML Editor add-on for their existing structured authoring software. Nothing wrong with using a MathML Editor but ASCII Math (http://asciimath.org/) is a great alternative as an easy-to-write markup language for mathematics … and it’s free!
tekAuthor offers both MathML and/or ASCII Markup to create equations. If using MathML, the equations need to be created in a MathML document and then re-used, or added into the document pages. With ASCII math the user can add the markup directly into the document pages.