% Dans le préambule
% -----------------
\usepackage{tikz}
% -----------------

\begin{tikzpicture}
\draw[dashed] (0,0)--(1,2);
\draw[->] (1,0)--(2,2)--(3,1);
\draw[line width=2pt, |->] (3,0)--(4,2);
\draw[{[-]},blue]  (4,0)--(3,2);
\end{tikzpicture}