The Locus Construction

The locus menu is used to construct the locus of a geometric object as a specified point moves along a one-dimensional path.  In the figure below we have constructed a circle c and have attached a point P to this circle. Then, we created another circle (in red) that has P  as its radius point.
locus 1

Now, we will construct the locus of the red circle with respect to P.  First, select the point P and then the circle c (in that order).  Click on the Locus menu. The "Construct" menu item will be active.  Select "Construct".  A set of images of the red circle will be displayed corresponding to uniformly distributed positions of the attached point P around circle c.

locus 2

If we now moved circle c or other points in the Canvas the locus would update automatically.  Also, to select the locus we just click on one of the copies of the red circle.  A locus is visually identified as selected when all copies of the locus object appear selected, as shown below.

locus 3

Once the locus is selected the "edit" menu item under the Locus menu will be active. If we select "Edit" a dialog box will pop-up permitting us to change the number of sample points that are used to position P around the circle. The default number of points is 25. Let's change this to 50.  After doing so, we get the following image.

locus 4