used standalone

tikz/dot-product-1/dot-product-1.tex

@@ -1,24 +1,18 @@
-\documentclass{article}
-\usepackage[pdftex,active,tightpage]{preview}
-\setlength\PreviewBorder{2mm}
+\documentclass[varwidth=true, border=2pt]{standalone}
 \usepackage{tikz}
 \usetikzlibrary{arrows,positioning} 
 \tikzset{
     %Define standard arrow tip
     >=stealth',
     % Define arrow style
-    pil/.style={
-           ->,
-           thick}
+    pil/.style={->,thick}
 }
 
 \begin{document}
-\begin{preview}
 \begin{tikzpicture}
     \draw[fill=green!30] (0,0) -- (90:.75cm) arc (90:27:.75cm);
     \draw[pil,color=black] (0,0) -- node[right=2pt] {$\vec a$} (27:2.2cm);
     \draw[pil,color=black] (0,0) -- node[near end, right=-3pt] {$\vec b$} (90:2cm);
     \draw(60:0.5cm) node {$\varphi$};
   \end{tikzpicture}
-\end{preview}
 \end{document}