set output 'beat_a.ps' 
set term postscript color enhanced 'Helvetica,18'  
set style line 1 lt rgb 'red' lw 3  
set style line 2 lt rgb 'green' lw 3  
set style line 3 lt rgb 'blue' lw 3  
set style line 4 lt rgb 'cyan' lw 3  
set style line 5 lt rgb 'violet' lw 3  
set grid 
set key top right 
set sample 1000 
set ylabel 'Height (m)'  
set xlabel 'Time (s)' 
set title '' 
plot [-30:30][-2.2:2.2] 1.0*sin(x)+1.0*sin(1.2*x)          with lines ls 1 lw 6 t ''  
set output 
quit 
