LaTex Error: Environment equation* undefined

Question

enter image description here

I am trying to work on a Poisson problem (BVP) which looks like the pic above. However, when I executed my codes as below, the compiler showed that

"LaTex Error: Environment equation* undefined."

I don't know why?

\begin{equation*}
(PE)\hspace{0.3cm}\left\{\begin{matrix}
\hspace{0.3cm} -\Delta u=f & in\hspace{0.1cm} \Omega  \\
\hspace{0.3cm} u(x)=0 & on \hspace{0.1cm} \partial \Omega
\end{matrix}\right.
\end{equation*}

Welcome to TeX.SX! It appears you're missing \usepackage{amsmath}. — egreg, Jun 30 '15 at 15:27
Once mathtools is loaded, you might be interested in the cases environment(s). — Johannes_B, Jun 30 '15 at 15:29
@TorbjørnT. Indeed, but mathtools provides some extensions to amsmath, that goes for cases as well. :-) — Johannes_B, Jun 30 '15 at 15:31

score 29 · Answer 1 · edited Jun 30 '15 at 17:12

29

Adding

\usepackage{amsmath}

to the preamble solved the problem.

edited Jun 30 '15 at 17:12

Werner

603,163

answered Jun 30 '15 at 15:39

ChiChou Huang

501

So, if I want to say personal gratitude to whom helped me to solve the problem, it is better to "Add Comment". right? – ChiChou Huang Jul 01 '15 at 17:07

LaTex Error: Environment equation* undefined

1 Answers1