This is a simulation of a four pendulum harmonograph using logo.
The successive positions are calculated using this formula:
x = ke-rt[sin(f1t + p1) + sin(f2t + p2)]
where k = 70 (makes the drawing fill the screen) r = .0001 (the "damping" factor) f1,f2,f3,f4 = pendulum frequencies p1,p2,p3,p4 = phase angles t = time (0,1,2,3,...,5000)The frequencies are assigned randomly from 0,1,...,10, the phase angles also but from 0,1,2,...359. These 8 numbers appear in the box for each drawing.