\documentclass[12pt]{article}
\usepackage{amssymb,amsmath,amscd,concmath,amsfonts}
\usepackage{color}
\pagestyle{empty}
\begin{document}
\begin{equation*}
  \text{gain}(\omega) = \frac{A_y}{A_u} = M \qquad
  \text{phase}(\omega) = \phi - \psi = \theta.
\end{equation*}
\end{document}