# Equations with text and math interpersed

This is related to the question I asked here:

Equations with only text in them

Basically I want to have an equation with a lot of text and some math in them. I don't want to use \mbox because there is a lot of text and it may start going out of the line. In the linked question a solution is provided using \parbox but I want to use math also in the middle.

For example:

$$\label{key} The product of two complex numbers z_1,z_2\in\mathbb{C} is given by the vector whose angle is the sum of the angles of the two complex numbers, i.e. arz(z_1z_2)=arg(z_1)+arg(z_2) and whose magnitude is the product of the magnitudes of the two complex numbers, i.e. |z_1z_2|=|z_1||z_2|$$


How do I accomplish this?

-
Wouldn't a theorem-like definition environment be more appropriate than an equation environment, here? (Hint: yes) – Jubobs Aug 12 '14 at 1:46
@Jubobs: How do I do that? – Shahab Aug 12 '14 at 2:01
@Jubobs: Can numbering be accomplished in such an environment in a manner similar to equations? – Shahab Aug 12 '14 at 2:12

May be you can do this.

\documentclass{article}
\usepackage{amsfonts}
\usepackage{calc}
\newlength{\mylen}
\setlength{\mylen}{\widthof{(99)}}
\begin{document}
$$\label{key} \left.\begin{minipage}{\dimexpr\textwidth-2\mylen\relax} The product of two complex numbers z_1, z_2\in\mathbb{C} is given by the vector whose angle is the sum of the angles of the two complex numbers, i.e. \arg(z_1z_2)=\arg(z_1)+\arg(z_2) and whose magnitude is the product of the magnitudes of the two complex numbers, i.e. |z_1z_2|=|z_1||z_2| \end{minipage} \right\}$$
\end{document}


The same can be done with \parbox too.

-

The "equation" in question contains not one but two entities that many people would interpret to be equations; moreover, both the text and the equations are very important. I therefore think you (and likely your paper's readers as well) would be better off if you chose a theorem-like environment to typeset the material, rather than insist on it being "just an equation".

This environment -- let's call it Statement for the sake of specificity -- can be cross-referenced easily. If you wish, you can use the equation counter to number the statement environments. An example of this usage is given below.

\documentclass{article}
\usepackage{amssymb,ntheorem}
\usepackage[noabbrev]{cleveref} % for "clever" cross-references
\theorembodyfont{\upshape} % choose \itshape if you prefer
\newtheorem{statement}[equation]{Statement}
\begin{document}
An equation:
$$\label{eq:pyth} a^2+b^2=c^2$$

\begin{statement}\label{complex-prod}
The product of two complex numbers $z_1,z_2\in\mathbb{C}$ is given by the vector whose
angle is the sum of the angles of the two complex numbers,
i.e.\ $\arg(z_1z_2)=\arg(z_1)+\arg(z_2)$ and whose magnitude is the product of the
magnitudes of the two complex numbers, i.e.\ $|z_1z_2|=|z_1||z_2|$.
\end{statement}

Another equation:
$$\label{eq:euler} \exp(i\pi)-1=0$$

As was shown in \cref{eq:euler,complex-prod,eq:pyth}, \ldots

\end{document}

-