%% 
%%  The LaTeX Graphics Companion, 2ed (first printing May 2007)
%% 
%%  Example 6-1-39 on page 331.
%% 
%%  Copyright (C) 2007 Michel Goossens, Frank Mittelbach, Denis Roegel, Sebastian Rahtz, Herbert Vo\ss 
%% 
%%  It may be distributed and/or modified under the conditions
%%  of the LaTeX Project Public License, either version 1.3
%%  of this license or (at your option) any later version.
%% 
%%  See http://www.latex-project.org/lppl.txt for details.
%% 

\documentclass{ttctexa}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{159.83385pt}
\StartShownPreambleCommands
\usepackage{pstricks,pst-plot}
\StopShownPreambleCommands
\begin{document}
\psset{xunit=0.025cm,yunit=4cm}
\begin{pspicture}(-0.1,-0.25)(190,1.1)
  \psgrid[subgriddiv=0,griddots=5,
     gridlabels=0pt,xunit=30,yunit=0.2](6,5)
  \psaxes[linewidth=1pt,ticks=none,Dx=30,
     Dy=0.2]{->}(190,1.1)
  \uput{0.5}[0](180,0){$\mathbf{\alpha}$}
  \uput{0.5}[90](0,1){$\mathbf{I/I_0}$}
  \psset{linewidth=1.5pt,linecolor=blue}
  \psplot{0}{180}{1 x 180 div sub 1
    6.28 div x 2 mul sin mul add abs sqrt}
  \psplot[linestyle=dashed]{90}{180}{
    2 x 90 div sub x 2 mul cos 2 add mul x
    2 mul sin 3 3.15 div mul add abs sqrt}
  \rput(50,0.75){$\varphi=0$}
  \rput(125,0.9){$\varphi=\pi/2$}
\end{pspicture}
\end{document}