c_s fix for D3Q7

	modified:   latex/supp_d3q7_defs.tex

latex/supp_d3q7_defs.tex

@@ -4,7 +4,7 @@ In $\mathbb{R}^3$, the position and velocity vectors are given by $\vx=(\x,\y,\z
 \subsection{Discrete velocity vectors}
 Discrete velocity vectors and the lattice speed of sound are defined by 
 \input{\path/d3q7_C}
-$$c_s = \frac1{{\sqrt{2}}},$$
+$$c_s = \frac12,$$
 respectively \cite{kruger}.
 
 %\begin{figure}[htb!]