The exterior derivative of a 1-form \(\omega\) in local coordinates is given by
\begin{equation*} d\omega= \sum_{i
\[
\newcommand{\d}{\mathrm{d}}
\newcommand{\e}{\mathrm{e}}
\newcommand{\i}{\mathrm{i}}
\]
One observe, that \(d\omega=0\) when \(\omega\) is a closed covector field
. This is a motivation of the exterior derivative.