### Line representation

A line is represented by a vector **u** and a moment; the latter
is a bivector **p^u** spanned by **u** and any position vector **p**
of a point on the line.

You can drag the endpoints of any of the vectors. Dragging **u** and **p**
changes the definition of the line, dragging **x** should convince you
that any point on the line indeed spans the same bivector with **u**.

Created with Cinderella
by Leo Dorst 20010712