# How continue an equation next line

How can continue the equation of the rectangle red in next line?

\documentclass[11pt,a4paper,twocolumn]{article}

...

\begin{equation*}
\left| \dot{r} \right| =
\sqrt{{- \, {e}^{-t} \left( \cos t + \sin t \right)}^{2} \, + \, {{e}^{-t} \left( \cos t + \sin t \right)}^{2} \, + \, {(- \, {e}^{-t})}^{2}}
\end{equation*}


• I would suggest to break the equation manually to control the output using an aligned environment and, the symbol & and \\. Have a look here – nikjohn Apr 10 '17 at 17:45
• @nikjohn hi, i already tried, problem is the root square. – Luis Apr 10 '17 at 17:52
• why not using something like the alignat* from mathtools (or amsmath) package? – user31729 Apr 10 '17 at 17:56
• @Luis If breaking the two-column format just for this equation is not something you would like, you could have a look here as to how to break the square root into multiple lines and still look good – nikjohn Apr 10 '17 at 17:58

I suggest using the multlined environment from mathtools to break the radicand . You also can choose not to break it, but to type in medsize (~80 % of \displaystyle) with the \mediummath command from nccmath. I took the opportunity to clean your code:

\documentclass[11pt,a4paper,twocolumn]{article}
\usepackage[utf8]{inputenc}
\usepackage{mathtools, nccmath}

\begin{document}

\begin{equation*}
\bigl| \dot{r} \bigr| =
\sqrt{\begin{multlined}[b] -\!\bigl(e^{-t} ( \cos t + \sin t )\bigr)^2 + \\ \bigl(e^{-t} (\cos t + \sin t)\bigr)^2 + \bigl(-e^{-t}\bigr)^2 \end{multlined}}
\end{equation*}
\begin{align*}
\bigl| \dot{r} \bigr| & =
\sqrt{\medmath{ -\!\bigl(e^{-t} ( \cos t + \sin t )\bigr)^2 + \bigl(e^{-t} (\cos t + \sin t)\bigr)^2 + \bigl(-e^{-t}\bigr)^2}} \\
& = \sqrt{ -\!\bigl(e^{-t} ( \cos t + \sin t )\bigr)^2 + \bigl(e^{-t} (\cos t + \sin t)\bigr)^2 + \bigl(-e^{-t}\bigr)^2}
\end{align*}

\end{document}


• Exactly what I was suggesting (about the first part of your answer)! – GuM Apr 10 '17 at 18:39
• Great minds think together! – Bernard Apr 10 '17 at 18:44
• Are you sure the entire term e^{-t}(\cos t + \sin t) should be squared? The OP's code seems to suggest that only (\cos t + \sin t) should be squared. (Of course, the OP's code might be in error...) – Mico Apr 10 '17 at 18:52
• @Mico: Not sure at all. That's the way I interpreted all those spurious { … }. Anyway, it's only a demo. – Bernard Apr 10 '17 at 19:13

As the equation* environment doesn't permit line breaks, consider using a multline* environment. And, instead of creating a multi-line surd expression with a \sqrt instruction, I suggest you use (...)^{1/2} notation.

Two additional comments about your code: Do try to use \left and \right less frequently, and don't needlessly encase various terms in curly braces.

\documentclass[11pt,a4paper,twocolumn]{article}
\usepackage{amsmath} % for 'multline*' env.
\begin{document}
...
\hrule % just to illustrate column width
\begin{multline*}
| \dot{r} | = \bigl\{
- e^{-t} ( \cos t + \sin t )^{2} \\
+ e^{-t} ( \cos t + \sin t )^{2}
+ (-e^{-t})^{2} \bigr\}^{1/2}
\end{multline*}
\end{document}


If you are interested in a square root expression and not a power notation that Mico's answer provides, have a look at the following code:

\begin{equation*}
\left| \dot{r} \right| =
\sqrt{
\begin{aligned}
&{- \, {e}^{-t} \left( \cos t + \sin t \right)}^{2} \, + \, \\
&{{e}^{-t}  \left( \cos t + \sin t \right)}^{2} \, + \, {(- \, {e}^{-t})}^{2}
\end{aligned}
}
\end{equation*}


## Ouptut

• Perhaps you could enhance readability by adding a \quad at the beginning of the second line. Edit: Also note that the mathtools package provides a multlined environment (maybe you already knew… :-) – GuM Apr 10 '17 at 18:23
• @GustavoMezzetti - I was not aware of that option since I do not usually encounter problems like this. It was a very helpful comment indeed – nikjohn Apr 10 '17 at 19:19
• Thanks for all your answers, apparently the root squared be cant to break. – Luis Apr 11 '17 at 1:51
• @nikjohn Off-topic, but seems that the surd is not perfectly connected to the line in the "Ouptut." Is there a way to avoid this? – L. F. Mar 4 '19 at 10:39