The simplest way to mix text and formulas in a Mathematica notebook is to put each kind of material in a separate cell. Sometimes, however, you may want to embed a formula within a cell of text, or vice versa.
|Ctrl+( or Ctrl+9||begin entering a formula within text, or text within a formula|
|Ctrl+) or Ctrl+0||end entering a formula within text, or text within a formula|
When you insert a formula in text, you can use the Convert to StandardForm and Convert to TraditionalForm menu items within the formula to convert it to StandardForm or TraditionalForm. StandardForm is normally appropriate whenever the formula is thought of as a Mathematica program fragment.
You should realize, however, that to make the detailed typography of typical formulas look as good as possible, Mathematica automatically does things such as inserting spaces around certain operators. But these kinds of adjustments can potentially be inappropriate if you use notation in very different ways from the ones Mathematica is expecting. In such cases, you may have to make detailed typographical adjustments by hand.