C.a.R.

The disadvantage of fixed circles is that they may become too small, so that the construction loses important features.

Demonstrate the effect of fixed circles on constructions as follows:

Drag A away from B, until the circles no longer intersect.
Note the perpendicular bisector disappears, because it is no longer valid.
To recover the perpendicular bisector, you may enlarge the circle around A. But before you can do this, you must "unfix" the circle. To do this, right click on the circle and uncheck the “Fixed” box in the "Edit circle" dialog box. Close the dialog box by clicking "OK".
Now right click on the circle and drag it to make it larger. When it is large enough to intersect the other circle, then the perpendicular bisector reappears.
This tutorial has no “Well Done!” screen.