\documentclass[12pt]{article} \pagestyle{empty} \begin{document} \begin{displaymath} p_{\rm trial}^{\rm arb}(\theta_{\rm g_a,f,p}) = p_{\rm trial}^{\rm ideal}(\theta_{\rm g_a,f,p}) = {{1}\over{2}} {\rm Sin}\left(\theta_{\rm g_a,f,p}\right) \end{displaymath} \end{document}