This is a STILL image.

It is NOT a movie.

The diagram shows the image of two points (S1 and S2) on the dark green circle.

It turns out that the position of the image of S2 can be found by applying an enlargement with centre at O, to point S1 (not S2), and that the position of the image of S1 can be found by applying the same enlargment to S2 (not S1).

In other words, the position of the image of the dark green circle can be found by enlarging the circle about O.

We can prove this by using this property of our inversion transformation:
OS1xOS'1 = OS2xOS'2.
This leads to OS'2/OS1 = OS'1/OS2, which gives us the scale factor of the enlargement.

Finally we present a task that allows us to apply some of our basic knowledge of the inversion transformation: PS