PRP TAN allows you to create a line perpendicular to the
first selected entity, and tangent to the second selected
entity. One entity can be a point; however, selecting two
points for this option causes an error message to be
displayed.

Select the first entity, near the point of 
perpendicularity.

Select the second entity, near the point of tangency.

An error message is displayed if you are constructing in 
3-D and the entities you select are not coplanar. You are
prompted to press <Enter> and to select the first entity.

If the points of perpendicularity and tangency are
coincident and the L-LIMIT switch is set to FUNCTN, an 
error message is displayed indicating that the current 
settings and selections result in a zero-length line. 
If this message is displayed, change the line limits and
press <Enter>, or reselect the desired entities.

With the L-LIMIT switch set to VIEWPORT, the line passes
through the points of perpendicularity and tangency, and
extends to the screen limits.
