Two damped oscillations draw a slowly closing weave. A second, slightly detuned pair opens the threads into folds — a mathematical version of a pendulum drawing machine.
Pendulum drawing · 19th century
Each coordinate is a sum of damped sine waves. Rational frequency ratios establish the figure; detuning makes successive loops drift apart. Damping contracts the trace, while the secondary pair gives the weave its depth. These are idealised small-angle pendulums.
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