TAN TAN allows you to create a line tangent to two 
selected entities. 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 tangency.
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 tangency points of the two entities 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 tangent line
passes through the tangency points, and extends to the
screen limits.
