## 4 Equations and Other Mathematical Environments

### 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.

### 4.2 Supported Environments

We can process all standard inline and single display style equation environments like

 $…$ \begin{displaymath} $$\begin{equation} $$…$$ … … … $…$ \end{displaymath}$$ \end{equation}

However, to let the Living Reviews popup equation referencing system work properly we cannot permit the following environments:

 \begin{subequations} \begin{eqaligntwo} … … \end{subequations} \end{eqaligntwo}

It is not allowed to use the \label command inside of an eqnarray* or an equation* environment (i.e. in the versions of the respective environments which suppress equation numbers). When such a label is referenced, this will lead to inserting wrong reference marks in the print as well as the onscreen versions of the article.

### 4.3 Examples

Equations within text paragraphs, , , are bracketed like that: $y = x^2$ or $$\sqrt{a^2 - b^2}$$.

If they are displayed, i.e. separated from the text,

use
$$\left[ \left( \frac{x^2}{n} - 1 \right) + \sin^2 \theta \right] = \ln x,$$
\begin{displaymath}
\Lambda = {\it \Gamma}^\lambda_{\mu \nu} + \mbox{\it O} \left(
\frac 1{x} \right),
\end{displaymath}

which generates equations without numbering, while

\begin{eqnarray}
E_{\mbox{\scriptsize tot}} = 1.5 \cdot 10^{53} \mbox{erg},
\label{equation:momentum}
\label{epubtk:eq1}\end{eqnarray}

displays equations numbers.

We recommend to use the LATEX display style for separated equations

\begin{eqnarray}
\left( \frac 1{x^2} \frac{\partial^2 x}{\partial t^2} + 1
\right) = \int_a^b x dr,
\label{equation:flux}
\label{epubtk:eq3}\end{eqnarray}

and text style for inline equations like :
$x / y = \int_a^b x dr$. This can also be enforced by \displaystyle and \textstyle resp.