LaTeX-examples/tikz/dot-product-3/dot-product-3.1.tex

\documentclass{article}
\usepackage{gensymb}
\usepackage[pdftex,active,tightpage]{preview}
\setlength\PreviewBorder{2mm}
\usepackage{tikz}
\usetikzlibrary{arrows,positioning,decorations.pathreplacing,shapes} 
\tikzset{
    %Define standard arrow tip
    >=stealth',
    % Define arrow style
    pil/.style={
           ->,
           thick}
}

\begin{document}
\begin{preview}
\begin{tikzpicture}
    \draw[pil] (0,0)   -- node[near end, above] {$\vec a$} (3cm, 0cm);
    \draw[pil] (0,0.5cm) -- node[near end, above] {$\vec b$} (2cm,0.5cm);
  \end{tikzpicture}
\end{preview}
\end{document}