I'm creating a styled notebook showing a simple theorem. I can set cell style as text or theorem or code to satisfy my requirement. But when I explain the theorem, I need to embed formula (not necessary for a whole line) into text. How can I do that. I didn't find any style for that.
Pretty easy: This is called an Inline Cell and you can start one with Ctrl+(. For the inline cell you can specify whatever style you like.
It seems Ctrl+9 is sufficient to start a new inline cell. The official shortcut listing says that you should type a (, therefore, I assumed that you need the Shift too.
I would like to expand a bit the answer of Vitaly Kaurov in the comments to the answer of halirutan. I type inline formulas usually as it is described in the halirutan answer. However, sometimes, though, rarely it does not work, and I need to apply the way Vitaly described. Then it may be done as follows:
So the difference with respect to what Vitaly proposed is that each formula is evaluated at once and there is no need to keep the list of the inline formulas.
In contrast to what I have written here I find that keeping a list of all the inline formulas used in the document, might be advantageous. Indeed, very often right after typing the formula in I find that it should be preferably shown in a slightly different way. It is faster to rewrite an already existing expression then to write it down anew.