Drawing vector summation parallelogram with TiKZ

Question

I'd like to draw something like this:

With two sides labeled, and the ability to label all four vertices, using TiKZ. How can this be done?

Answer 1

\documentclass[tikz,border=3mm]{standalone}
\begin{document}
\begin{tikzpicture}[dot/.style = {circle, fill, minimum size=3pt, inner sep=0pt,
    label={[blue,font=\sffamily]above right:#1},alias=#1}]
  \path foreach \X/\Y in {120/A,60/B,0/C}{(\X:4) node[dot=\Y]{}}
  (0,0) coordinate (O)
  foreach \X/\Y/\Z in {blue/A/bd,red/B/bd,green!70!black/C/ad}
  { (O) edge[\X,-latex,edge label={$v_{\Z}$}] (\Y)}
  (B) edge[dashed] (A)  edge[dashed] (C);
\end{tikzpicture}
\end{document}