Mathematica notebooks fully support standard mathematical notation--for both output and input.
Mathematica combines the compactness of mathematical notation with the precision of a computer language.
Mathematica's StandardForm is precise and unambiguous. TraditionalForm requires heuristics for interpretation.
Look at the Formula Gallery for other examples of mathematical formulas generated by Mathematica.
Mathematica supports over 700 special characters with new fonts optimized for both screen and printer. You can find all these characters in the Complete Characters palette. All of them have consistent full names; some also have aliases and TeX names.
Mathematica includes full support for MathML.