Thanks Paulo, this is most helpful!

]]>Thanks Berend. Some difficulty with cut&paste… And I could not fix it earlier because of the “Shanghai incident”!

]]>Line with if (bb[2] theta}

gives a syntax error.

The symbol tes in function dthe and the following plot is not defined.

]]>Place the origin of a cartesian system at the centre of the first disc. For simplicity, suppose that at the centre of the second disc has coordinates . Consider the point at the second disk which has coordinates at $t=0$. The movement of this point is described by the vector , where

and .

Then, after some algebra, the magnitude of the speed is

If we make in the last expression we recover the familiar .

All my best,

Paulo.

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