% Windshield wiper - drawing for calculating the area swept by the blade
% Author: Jimi Oke
\documentclass{article}
\usepackage[margin=2cm]{geometry}
\usepackage{tikz}
%%%<
\usepackage{verbatim}
\usepackage[active,tightpage]{preview}
\PreviewEnvironment{tikzpicture}
\setlength\PreviewBorder{5pt}
%%%>
\begin{comment}
:Title: Windshield wiper
:Tags: Mathematics; Geometry
:Author: Jimi Oke
:Slug: windshield-wiper
A windshield or windscreen is the front window of a car, a bus,
or an aircraft, for example. Wipers are used for removing rain and
debris from it. This drawing has been made for students who were
calculating the area swept by the blade of the wiper.
\end{comment}
\usetikzlibrary{fadings}
\begin{document}
\begin{tikzpicture}[>=latex]
    \tikzfading[name=fade out, inner color=transparent!0,
         outer color=transparent!100]

    % dimensions and angle
    \draw[|<->|, xshift=0.1cm,yshift=-0.4cm] 
    (15:0) -- (15:6) node[fill=white, midway,sloped] {36 in} ;

    \draw[|<->|, xshift=-0.15cm,yshift=-0.4cm] 
    (155:0) -- (155:2) node[fill=white, midway,sloped] {12 in} ;

    \draw[<-] (15:.6) arc (15:155:.6) ;
    \node at (45:1.1) {$0.8\pi$} ;

    % background/shading
    \fill [gray, path fading=fade out] (-8,-2) rectangle (9,8);

    % sweep area
    \filldraw[gray!50,left color=blue!25, right color=blue!30, middle color=white] 
    (15:2) arc (15:155:2) -- (155:2) -- (155:6) arc (155:15:6) -- (15:2) ;

    \draw[dashed] (15:0) -- (15:2) ;
    \draw[dashed] (155:0) -- (155:2) ;
    
    % wiper blade
    \filldraw(0,0) circle (.08cm) ;
    \filldraw[very thick,black,double distance=1pt] (92:0) -- (92:2.2) ;
    \draw[ultra thick] (90:2) -- (90:6) ;
    \draw[fill=gray!90!blue] (90.5:2.2) -- (94:2.2) -- (91.5:5.5) --
    (90.5:5.5);
    \draw[fill=gray!90!blue]  (90:5.5) -- (91:5.5) -- (90.5:6) --
    (90:6); 
\end{tikzpicture}
\end{document}