# Help with aligning equations

Can anyone, please, help me with a code to align the equations the same as the picture attached ?

I have tried to insert a big bracket to cover the two equations on the left side image but i do not know why my bracket cover just one equation.

Sincerely regards, Sérgio

Replay

Here is a simple way to achieve this:

\documentclass{article}

\usepackage{amsmath,amstext}
\usepackage{newtxmath}
\begin{document}

\begin{equation}
\begin{cases}
\displaystyle
\nu(z_0)+\frac{g}{f}\frac{\partial\,\eta_s}{\partial\,x}
=\frac{g}{f}\frac{\partial\,\eta}{\partial\,x}\\[15pt]
\displaystyle\text{with }\nu(z_0) =
\frac{1}{f\rho_0}\frac{\partial\,P_{z0}}{\partial\,x}
\end{cases}
\Rightarrow \eta = \eta_s+ \frac{P_{z0}}{\rho_0g}
\end{equation}

\end{document}



Output:

Using amsmath

\documentclass{article}
\usepackage{amsmath}

\begin{document}
If you want it center-aligned inside the braces, use \texttt{gathered}
\begin{equation}
\left\{
\begin{gathered}
v(z_0) + \frac{g}{f} \frac{\partial\eta_s}{\partial x} = \frac{g}{f} \frac{\partial \eta}{\partial x} \\
\text{with } v(z_0) = \frac{1}{f\rho_0} \frac{\partial P_{z0}}{\partial x} \text{ (junk to show alignment)}
\end{gathered}
\right. \implies \eta = \eta_s + \frac{P_{z0}}{\rho_0 g}
\end{equation}

If you want it either left-aligned, it is slightly simpler:
\begin{equation}
\begin{cases}
v(z_0) + \frac{g}{f} \frac{\partial\eta_s}{\partial x} = \frac{g}{f} \frac{\partial \eta}{\partial x} \\
\text{with } v(z_0) = \frac{1}{f\rho_0} \frac{\partial P_{z0}}{\partial x} \text{ (junk to show alignment)}
\end{cases}
\implies \eta = \eta_s + \frac{P_{z0}}{\rho_0 g}
\end{equation}

If for some reason you want it right aligned, you can use \texttt{aligned}

\begin{equation}
\left\{
\begin{aligned}
v(z_0) + \frac{g}{f} \frac{\partial\eta_s}{\partial x} = \frac{g}{f} \frac{\partial \eta}{\partial x} \\
\text{with } v(z_0) = \frac{1}{f\rho_0} \frac{\partial P_{z0}}{\partial x} \text{ (junk to show alignment)}
\end{aligned}
\right. \implies \eta = \eta_s + \frac{P_{z0}}{\rho_0 g}
\end{equation}

\end{document}



I would do it this way, using the dcases and rcases environment from mathtools. Also, the esdiff package simplifies typing (partial) derivatives.

\documentclass{article}

\usepackage{mathtools}
\usepackage{fourier, erewhon}
\usepackage{esdiff}

\begin{document}

\begin{equation}
\begin{rcases}\begin{dcases}
ν(z₀)+\frac{g}{f}\diffp{\eta_s}{x}
=\frac{g}{f}\diffp{η}{x}\\[0.5ex]
\text{with }ν(z₀) =
\frac{1}{f\rho₀}\diffp{P_{z0}}{x}
\end{dcases}\end{rcases}
⇒ η= \eta_s+ \frac{P_{z0}}{\rho₀g}
\end{equation}

\end{document}


Category: equations Time: 2016-07-28 Views: 0