# How can I add left aligned text to an equation?

I have a document I am trying to copy to learn TeX. Here is what I have encountered: How can I have the "or" in the equation. This is what I have right now:

$f = ma;$
But $a$ is the change in velocity,

$f = m \frac{dv}{dt};$
$f = m \frac{d^2y}{dt^2};$


Edit: Trying out Stefan's answer

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– Peter Grill Jun 15 '12 at 17:30

## 1 Answer

Use the amsmath package and the commands \text{...} for text in the formula or \intertext{...} for text between the lines of multi-line formulas. For example:

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{align*}
f &= ma;\\
\intertext{But $a$ is the change in velocity}
f &= m \frac{dv}{dt};\\
\intertext{or}
f &= m  \frac{d^2y}{dt^2};
\end{align*}
\end{document}


One advantage of align* to $...$ is that you can align the equations on relation symbols.

If you wish to put or in the same line, you could use \text and flalign* :

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{flalign*}
&& f &= ma;&\\
\text{or} && f &= m \frac{dv}{dt};&\\
\text{or}  &&f &= m  \frac{d^2y}{dt^2};
\end{flalign*}
\end{document}


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It dosn't work. It still gives me spaces in between. Check my original post for a picture. – masfenix Aug 13 '10 at 16:16
Sorry, can you explain what the $$ does – masfenix Aug 13 '10 at 16:22  opens and closes the inline math mode.$$ opens and closes displayed math mode. Both are TeX commands, not LaTeX. Or do you mean the && ? – Stefan Kottwitz Aug 13 '10 at 16:24
oh, yea sorry. I meant teh && – masfenix Aug 13 '10 at 16:27
& is used both for specifying the alignment position and as column separator, alternating. In columns of formulas, &= means that at = would be aligned, a following & would end the column, like in a table. && has been used to skip a column, i.e. to create an empty column. – Stefan Kottwitz Aug 13 '10 at 16:53