\documentclass[a4paper,fleqn]{report}
\usepackage{amsmath}
\setlength{\mathindent}{1cm}
\begin{document}
\noindent Euler's formula is given below:
\begin{equation*}
e^{ix} = \cos{x} + i \sin{x}
\end{equation*}
\noindent This is a very important formula.
\end{document}