# Changing vertical spacing between equations

I'd like to reduce vertical spacing between dmath equations. I don't know how spacing works here. I tried changing line spacing with setspace but to no effect. This is meant to be a formula sheet with many stacked equations. One of the possible ways to go about this is to use dgroup.

\documentclass[a4paper,landscape]{article}
\usepackage{amsmath}
\usepackage{breqn}

\begin{document}
\begin{dmath}
Q(\lambda,\hat{\lambda}) = -\frac{1}{2} P{(O \mid \lambda )} \sum_s \sum_m \sum_t             \gamma_m^{(s)} (t) \left( n \log(2 \pi ) + \log \left| C_m^{(s)} \right| + \left(    \mathbf{o}_t - \hat{\mu}_m^{(s)} \right) ^T C_m^{(s)-1} \left(\mathbf{o}_t -   \hat{\mu}_m^{(s)}\right) \right)
\end{dmath}
\begin{dmath}
Q(\lambda,\hat{\lambda}) = -\frac{1}{2} P{(O \mid \lambda )} \sum_s \sum_m \sum_t             \gamma_m^{(s)} (t) \left( n \log(2 \pi ) + \log \left| C_m^{(s)} \right| + \left(    \mathbf{o}_t - \hat{\mu}_m^{(s)} \right) ^T C_m^{(s)-1} \left(\mathbf{o}_t -   \hat{\mu}_m^{(s)}\right) \right)
\end{dmath}
\end{document}

• You should make these two dmath equations into one align. – Werner Feb 3 '14 at 20:14
• You should enclose the two dmath alignments inside a dgroup* environment. The result that's obtained, though, confirms me in the opinion that breqn is to be kept as far away as possible from my documents. – egreg Feb 3 '14 at 20:59
• I agree with @egreg, I couldn't find any options at all that gave good breaks automatically for this example. Far, far better to use one of the amsmath environments and break the equations manually. – Dan Feb 3 '14 at 22:29
• You can manually add a \vspace{-1em} prior to entering the 2nd dmath environment. – Steven B. Segletes Feb 14 '14 at 1:36

As people have mentioned dgroup is pretty much the only way. However, I found using breqn to be inconvenient. It still requires intervention, because equations are not broken up the way I would like. So, now I'm using gather* with split.