4.1 Fonts

TEX uses glyphs from the slanted font family for letters in math mode by default. If symbols should be represented by upright roman letters, this can be indicated by passing the characters as argument to the \mathrm command. Typically this is done to distinguish operators from operands as in
created from

\mathrm{log} a

Note: Using the font selector \rm provided by LATEX 2.09 will not work in math mode.