2 PTS allows you to define the directrix by indicating two
positions as its endpoints.

Indicate a position for the first endpoint of the
directrix, using a Position Menu option.

Indicate a position for the second endpoint of the
directrix, using a Position Menu option.

After defining the directrix, indicate a focal point for 
the parabola, using a Position Menu option.

Indicate the start point for the parabola, using a 
Position Menu option. If the indicated point is not on 
the parabola, the program determines the start point by 
constructing a line that is perpendicular to the parabola
and passes through the indicated point. The intersection
of the parabola and the perpendicular line is used as the
start point.

Indicate the endpoint for the parabola, using a Position
Menu option. If the indicated point is not on the 
parabola, the program determines the endpoint in the 
manner that was described for the start point.

If the parabola cannot be created, an error message is
displayed. You are prompted to press <Enter> and to 
redefine the parabola, beginning with the directrix.

In 2-D construction mode, the directrix, the focal point,
and the start and endpoints are projected to the current
construction plane. The parabola is created in the current
construction view, at the current depth.

In 3-D construction mode, the parabola is created in the
plane that is defined by the directrix and the focus.
