I am new to LaTeX and I was using the amsthm package in order to write proofs by using the proof environment:

```
\documentclass{book}
\usepackage{amsthm}
\newtheorem{theorem}{Theorem}
\begin{document}
\begin{theorem}
Stuff in here
\end{theorem}
\begin{proof}
Proof in here
\end{proof}
\end{document}
```

I then decided to use the mathtools package, since it contains more symbols and corrects some of the amsthm's bugs. However, if I substitute the line

```
\usepackage{amsthm}
```

for

```
\usepackage{mathtools}
```

I get the error "! LaTeX Error: Environment proof undefined."

Is there a way to correct this?

Thanks for helping!

## Best Answer

`amsthm`

and`mathtools`

are unrelated.`mathtools`

updates and extends`amsmath`

.you still need

`amsthm`

if you want the`proof`

environment.