TAN/PRP (tangent/perpendicular) allows you to create a 
line tangent and/or perpendicular to two entities, or 
to an entity and a position.

It is possible to create the entity by choosing from
the following options:


TAN PT - to create a line tangent to a selected entity, 
and through a specified reference point.

PRP PT - to create a line perpendicular to a selected
entity, and through a specified point.

TAN TAN - to create a line tangent to two selected 
entities. One of the entities can be a point; however, an
error message is displayed if you select two points.

TAN PRP - to create a line tangent to the first selected
entity, and perpendicular to the second selected entity. 
One of the entities can be a point; however, an error
message is displayed if you select two points.

PRP TAN - to create a line perpendicular to the first
selected entity, and tangent to the second selected
entity. One of the entities can be a point; however, an
error message is displayed if you select two points.

PRP PRP - to create a line perpendicular to two selected
entities. One entity can be a point; however, an error
message is displayed if you select two points.

In 2-D construction mode, selected construction entities
and reference points must be coplanar. 

In 2-D construction mode, the reference entities are
projected to the current construction plane, and the line 
is created in the construction plane.

In 3-D construction mode, you cannot select polylines,
polygons, and 3-D splines because they are not planar
entities.

In 3-D construction mode, the line is created in the plane
that is defined by the selected entities.

The length of the new line is determined by the L-LIMIT
(line limits) switch setting. Line limits are set by
selecting the CONTROL, L-LIMIT option from the Main Menu.
