%% 
%%  A DANTE-Edition example
%% 
%%  Example 15-03-3 on page 206.
%% 
%%  Copyright (C) 2011 Herbert Voss
%% 
%%  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.
%% 
%% 
%% ==== 
% Show page(s) 1
%% 
\documentclass[]{article}
\pagestyle{empty}
\setlength\textwidth{375.57637pt}
\setlength\parindent{0pt}
\AtBeginDocument{%
  \psset{mathLabel=false,labelFontSize=\small}}

\usepackage{pst-plot} \psset{xunit=0.02cm,yunit=3cm}

\begin{document}
\begin{pspicture}(-0.1,-0.1)(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)%
    [$\mathbf{\alpha}$,0][$\mathbf{I/I_0}$,90]
 \psplot[linewidth=1.5pt,algebraic,xunit=57.325]{0}{Pi}{sqrt(1-x/Pi+sin(2*x)/(2*Pi))}
 \psplot[linewidth=1.5pt,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*(40,0.85){$\varphi=0$}  \rput*(125,0.9){$\varphi=\pi/2$}
\end{pspicture}
\end{document}