documentclass[11pt]{article}
usepackage{setspace}
usepackage[a4paper]{geometry}
usepackage[utf8]{inputenc}
usepackage[english]{babel}
usepackage{amsmath}
usepackage{mathrsfs}
usepackage{amssymb}
input{Definitions and Macros.tex}
begin{document}
begin{equation}
fnt sim f^*
end{equation}

end{document}