Please explain the logic used to construct the plot below.

plots:-implicitplot(r >= cos(theta), r = 0 .. 1/3, theta = 0 .. 2*Pi, filledregions, coords = polar, numpoints = 5000, scaling = constrained)

The help page for dsolve,numeric,events says that "A call to a procedure-form dsolve numeric procedure" can return the time that one or more events fired by coding the eventfire option.

I do not know how to code for this.

Please provide a simple example of a procedure-form dsolve numeric with an event that exhibits this feature.

For a spring hanging vertically from a fixed point, suppose the spring constant, k, is a function of the distance from the fixed point to the other (lowest) end of the spring (for example; the diameter of the spring's coils changes along the length of the spring) .

What ODE reflecting this situation will yield solutions for the harmonic motion of the spring after it is stretched from its equilibrium position?

https://www.maplesoft.com/applications/view.aspx?SID=3707

The worksheet below animates a hamster running back and forth on a linear floor within a wheel. Its motion is such that the wheel remains stationary.

What math would describe the hamster running back and forth such that the wheel oscillates with a constant frequency and the floor's vertical angle oscillates between plus and minus an angle greater than zero and less than 2 Pi?

Hamster_in_wheel.mw