A function of the coordinates which is constant along a trajectory in phase space. The number of degrees of freedom of a dynamical system such as the Duffing differential equation can be decreased by one if an integral of motion can be found. In general, it is very difficult to discover integrals of motion.
Integral of Motion
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Cite this as:
Weisstein, Eric W. "Integral of Motion." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/IntegralofMotion.html