Problem of the Week

March 29, 2010

Consider two points, P and Q, in the coordinate plane. Draw a line l through P and a line m, not parallel to l, through Q. Now let l and m rotate counterclockwise about P and Q, respectively, at the same speed (say one revolution per minute). At each moment, l and m intersect at some point.

What shape do these intersection points make when you consider them all at once?