## B.7  Mathematical Formulae

\hat{\mu} = \hat{\Delta}.

In text: $\hat{\mu} = \hat{\delta}$

An you get, displayed:

 ^ µ
=
 ^ Δ
.

In text: µ^ = δ^.

Whereas, with the default of \hat being \^, you get “µ = δ”, with the following warnings:

./tmp.tex:4652: Warning: Application of '\^' on '\mu' failed
./tmp.tex:4652: Warning: Application of '\^' on '\delta' failed

The \vec command is rendered differently in display and non-display mode. In display mode, the arrow appears in normal position, while in non-display the arrow appears as an ordinary superscript.

\vec{u} in text mode: u,   \vec{u} in display mode:
 → u

Most “extensible accents” (\widetilde, \widehat, etc.) are not even defined. There are a few exceptions: line “accents”:

 abc
\underline

 abc
\overline

Brace “accents”:

 1 × 2 × ⋯ × n ◥ ▼ ◤
\underbrace

 ◢ ▲ ◣ 1 × 2 × ⋯ × n
\overbrace

And arrow “accents”:

 ◂ 1 × 2 × ⋯ × n
\overleftarrow

 ▸ 1 × 2 × ⋯ × n
\overrightarrow

### B.7.7  Spacing

By contrast with LATEX, space in the input matters in math mode. One or more spaces are translated to one space. Furthermore, spaces after commands (such as \alpha) are echoed except for invisible commands (such as \tt). This allows users to control space in their formulas, output being near to what can be expected.

Explicit spacing commands (\,, \!, \: and \;) are recognized, the first two commands do nothing, while the others two output one space.

### B.7.8  Changing Style

Letters are italicized inside math mode and this cannot be changed. The appearance of other symbols can be changed using LATEX 2є style changing commands (\mathbf, etc.). The commands \boldmath and \unboldmath are not recognized. Whether symbols belonging to the symbol font are affected by style changes or not is browser dependent.

The \cal declaration and the \mathcal command (that yield calligraphic letters in LATEX) exist. They yield red letters by default.

Observe that this does not corresponds directly to how LATEX manage style in math mode and that, in fact, style cannot really change in math mode.

Math style changing declarations \displaystyle and \textstyle do nothing when HEVEA is already in the requested mode, otherwise they issue a warning. This is so because HEVEA implements displayed maths as tables, which require to be both opened and closed and introduce line breaks in the output. As a consequence, warnings on \displaystyle are to be taken seriously.

The commands \scriptstyle and \scriptscriptstyle perform type size changes.