mathtools: cases inside alignment
Solution 1
Here is a solution with cases
. I've added another solution, which has a better vertical spacing, in my opinion, and a shorter code, with the empheq
package (which loads mathtools
).
Also I replaced \triangle
with the more correct Delta
, and defined div
as a Math Operator:
\documentclass{article}
\usepackage{empheq}
\DeclareMathOperator{\Div}{div}
\begin{document}
\[
\begin{dcases}
\begin{aligned}
-\Delta u +\nabla p & =-w\cdot \nabla w +f \\
\Div u & =0 \\
u & =0
\end{aligned}
&
\begin{aligned}
& \text{in } \Omega, \\
& \text{in } \Omega, \\
& \text{on }\partial \Omega.
\end{aligned}
\end{dcases}
\]
\bigskip
\begin{empheq}[left = \empheqlbrace]{alignat* = 2}
-\Delta u +\nabla p & =-w\cdot \nabla w +f &\quad & \text{in } \Omega, \\
\Div u & = 0&\quad & \text{in } \Omega, \\
u & =0 & & \text{on }\partial \Omega.
\end{empheq}
\end{document}
Solution 2
You can use aligned
inside cases
, but I'd prefer not to align at the equals signs.
\documentclass{article}
\usepackage{mathtools}
\DeclareMathOperator{\Div}{div}
\begin{document}
With alignment at the equals sign:
\[
\begin{cases}
\begin{aligned}
-\triangle u +u \cdot \nabla u +\nabla p &= f && \text{in $\Omega$}, \\
\Div u &= 0 && \text{in $\Omega$}, \\
u &= 0 && \text{on $\partial \Omega$},
\end{aligned}
\end{cases}
\]
Without alignment:
\[
\begin{dcases*}
-\triangle u +u \cdot \nabla u +\nabla p = f & in $\Omega$, \\
\Div u = 0 & in $\Omega$, \\
u = 0 & on $\partial \Omega$,
\end{dcases*}
\]
\end{document}
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Will Kwon
Brief introduction about me I'm currently studying the theory of partial differential equation.
Updated on August 01, 2022Comments
-
Will Kwon over 1 year
Hi. I have struggled with aligning with cases environment The minimal example of the above thing is the following:
\documentclass{article} \usepackage{mathtools} \makeatletter \newcases{PDEcases}{\quad}{% \hfil$\m@th\displaystyle{##}$}{{##}\hfil}{\lbrace}{.} \makeatother \begin{document} \[ \begin{PDEcases} -\triangle u +u \cdot \nabla u +\nabla p =f&in $\Omega$\\ \mathrm{div}\, u =0& in $\Omega$\\ u=0& on $\partial \Omega$, \end{PDEcases} \] Alignment inside cases \[ \begin{dcases*} -\triangle u +\nabla p =-w\cdot \nabla w +f&in $\Omega$\\ \hspace{2.75em}\mathrm{div}\, u =0& in $\Omega$\\ \hspace{4.2em}u=0& on $\partial \Omega$, \end{dcases*} \] \end{document}
For the first case, using
\newcases
, I can easily make a custom environment on cases. But I want to make an equation like second form. But I failed to make an equation with cases environment. I manually adjust it by using\hspace
.How can I make it more smarter way?
One possible solution of mine is to use the alignedat enviornment. But it is not a case environment.
Here is a code:
\[ \left\{ \begin{alignedat}{2} -\triangle u +\nabla p &=-w\cdot \nabla w +f&&\qquad \mbox{in $\Omega$},\\ \mathrm{div}\, u &=0&&\qquad \mbox{in $\Omega$},\\ u&=0 &&\qquad \mbox{on $\partial \Omega$}, \end{alignedat} \right. \]
I'm unsatisfied with
\quad
part and\left\{ \right.
Is there anyway to make it using cases stuff?Thanks in advances
-
Will Kwon almost 6 yearsActually, my society denote Laplacian by \triangle. Thanks! This is really nice.