<HTML><FONT FACE=arial,helvetica><HTML><FONT SIZE=2 PTSIZE=10 FAMILY="SANSSERIF" FACE="Arial" LANG="1">Here is an example which allows to draw J_n (But without guarantee).<BR>
<BR>
\documentclass[a4paper]{article}<BR>
\usepackage{pstcol}<BR>
\usepackage{pst-plot}<BR>
% Bessel Jn 4 août 2002<BR>
% Manuel LUQUE <BR>
\def\Bessel#1{%<BR>
%#1 = n<BR>
\parametricplot[plotpoints=1000]{-20}{20}{%<BR>
/J1 0 def<BR>
/xBessel t 180 mul 3.14159 div def<BR>
0 0.1 180 {<BR>
/tB exch 180 mul 3.14159 div def<BR>
/J1 J1 0.1 xBessel<BR>
tB sin mul tB #1 mul sub cos mul add def<BR>
} for<BR>
t J1 180 div}<BR>
}<BR>
\begin{document}<BR>
$$J_n(x)=\frac{1}{\pi}\int_0^\pi\cos(x\sin t-nt)\mathrm{d}t$$<BR>
\psset{xunit=0.4,yunit=10}<BR>
\begin{pspicture}(-10,-0.8)(10,0.8)<BR>
%\psgrid[gridlabels=0pt](0,0)(-20,-1)(20,1)<BR>
\psset{linecolor=red}<BR>
\Bessel{0}<BR>
\psset{linecolor=blue}<BR>
\Bessel{1}<BR>
\psset{linecolor=green}<BR>
\Bessel{2}<BR>
\psset{linecolor=magenta}<BR>
\Bessel{3}<BR>
\psaxes[Dy=0.1](0,0)(-20,-1)(20,1)<BR>
\end{pspicture}<BR>
\end{document}<BR>
<BR>
Manuel<BR>
</FONT></HTML>