# Elementary differential equations 7th edition - Boyce W.E

ISBN 0-471-31999-6

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Viscous damping A body moving through air (or some other medium) is slowed down by a resistive force that acts opposite to the body’s velocity, v. In viscous

damping (or viscous drag), the force is proportional to the velocity:

force = —kv for some positive constant k.

Wada property The Wada property, as described and illustrated on Screen 3.2 of Module 12 is the fact that:

Any point on the boundary of any one of the areas described on Screen 3.2 is also on the boundary of all the others.

The geometry/topology example constructed by Wada was the first to have this property; we can now show that the basins of attraction for our forced, damped pendulum ODE have the same property. See Module 12 and Chapter 12.

All we know about Wada is that a Japanese manuscript asserts that someone by that name is responsible for constructing this example, showing that for three areas in a plane, they can become so utterly tangled that every boundary point touches all three areas!

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