Title: Implies sign between two lines
Tags: math-mode
Question: I would like to achieve the below effect:

I was able to achieve something little bit similar with the following code, however it is a wrong solution.
```\begin{ceqn}
\begin{equation*}
\begin{gathered}
x_{1}=h \\
x_{2}=\dot{h} \\
\downarrow \\
\dot{x_{1}} = x_{2}\\
\dot{x_{2}} = u
\end{gathered}
\end{equation*}
\end{ceqn}
```
My wrong solution:

Could you please let me know how to achieve the desired effect?
Thank you in advance!

Comment: Notice that `\dot{x_{1}}` is different than `\dot{x}_{1}`. You probably want to use the latter.

Here is the accepted answer: ```\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation*}
\begin{aligned}
x_1&amp;=p\\
x_2&amp;=\dot{p}
\end{aligned}
\quad\Rightarrow\quad
\begin{aligned}
\dot{x}_1&amp;=x_2\\
\dot{x}_2&amp;=u
\end{aligned}
\end{equation*}
\end{document}
```




Here is another answer: A simple version (you might need to adjust spacing):



```\documentclass{article}

\usepackage{amsmath}

\begin{document}
\[
\begin{gathered}
x = y\\
y = x
\end{gathered} \Rightarrow \begin{gathered}
x = y\\
y = x
\end{gathered}
\]
\end{document}
```


{'source': 'StackExchangeDataset', 'subset': 'tex.stackexchange.com', 'metadata': {'AnswerCount': 2, 'CommentCount': 1, 'ContentLicense': 'CC BY-SA 3.0', 'CreationDate': '2017:00:11/26/17', 'FavoriteCount': None, 'PostTypeId': 1, 'Tags': '<math-mode>', 'Title': 'Implies sign between two lines', 'ViewCount': 977, 'id': 403172, 'user_AboutMe': None, 'user_AccountId': 6789227.0, 'user_DisplayName': 'hunsnowboarder', 'user_Reputation': 97.0, 'user_Views': 40.0, 'user_id': 133854.0}}