# Long Subequation in LaTeX

I'm using the amsmath package, in the subequations environment I have the following set of equations

\begin{subequations}
\begin{align}
&\rho\left(u\frac{\partial u}{\partial x}+v\frac{\partial u}{\partial r}\right)=-\frac{\partial P}{\partial x}+\frac{M^2_\infty}{Re}\frac{1}{r}\frac{\partial}{\partial r}\left(\mu r\frac{\partial u}{\partial r}\right)\\
&\rho\left(u\frac{\partial h}{\partial x}+v\frac{\partial h}{\partial r}\right)=\rho\left(u\frac{\partial P}{\partial x}+v\frac{\partial P}{\partial r}\right)+\frac{M^2_\infty}{Re\dot Pr}\frac{1}{r}\frac{\partial}{\partial r}\left(\mu r\frac{\partial h}{\partial r}\right)+\frac{M^2_\infty}{Re}\mu\left(\frac{\partial u}{\partial r}\right)^2
\end{align}
\end{subequations}


Using this code, the reference for the second equation is pushed to the line below. What I'm trying to figure out is how to send

+\frac{M^2_\infty}{Re}\mu\left(\frac{\partial u}{\partial r}\right)^2


onto another line, aline it with the equals signs without it gaining it's own equation reference.

Any ideas?

• add \notag to the line that should not get a number – daleif Jun 14 '13 at 14:52
• Welcome to TeX.SX! – mafp Jun 14 '13 at 15:09

Use the split environment, it works like align

\begin{subequations}
\begin{align}
\rho\left(u\frac{\partial u}{\partial x}+v\frac{\partial u}{\partial r}\right)
&= -\frac{\partial P}{\partial x} +
\frac{M^2_\infty}{Re}\frac{1}{r}\frac{\partial}{\partial r}\left(\mu
r\frac{\partial u}{\partial r}\right)\\
\begin{split}
\rho\left(u\frac{\partial h}{\partial x} + v \frac{\partial h}{\partial r}
\right) &= \rho \left( u\frac{\partial P}{\partial x} + v
\frac{\partial P}{\partial r} \right) \\

• i'd suggest the following minor changes: in the second (split) subequation, make the line break after the first, rather than the second, parenthesized expression on the right-hand side, and introduce a \quad{} after the & following the line break, so that the plus is set below the \rho instead of below the equal sign. (the {} will enforce the correct spacing after the plus.) – barbara beeton Jun 14 '13 at 15:04