\documentclass{article}
\usepackage{physics}
\usepackage{witharrows}

\begin{document}

\begin{DispWithArrows}
  \dv{i_2}{t} &= - \frac{M}{L_2} \dv{i_1}{t}
  \Arrow{par intégration} \\
  \Rightarrow
  i_2 &= -\frac{M}{L_2}i_1 + \mathrm{cte}
\end{DispWithArrows}

\end{document}
