A brief comment…
From time to time, when writing in LaTeX, one repeats a mathematical expression over and over. A shortcut for this is to define a newcommand using,
In the above example, the capital R denoting real numbers is re-defined through the command
\R. However, every time one’d like to call the command inside the text the dollar signs should be written, i.e.,
A way for avoiding the dollar signs is to use the ensuremath command,
which allows to write just
\R in both, math and text mode.