functions in demo3.i -

             demo3  
 
     Solve Lagrange's equations for a famous chaotic pendulum (as on  
     exhibit at the San Francisco Exploratorium).  Run a movie of the  
     result.  By default, the movie runs for 60 seconds, but if you  
     supply an argument to the demo3 function, it will run for that  
     many seconds.  
     The kick= keyword may be used to adjsut the initial amplitude;  
     kick= 1.2 is the default.  
     You may also wish to supply a damp_time= keyword to see the effect  
     of an ad hoc damping term.  damp_time=100 is nice.