DOUBLE allows you to trim or extend an entity (including
circles) to two entities by selecting the portion of the
entity to keep. This function is view dependent.

Select the portion of the trim or extend entity that is to
remain.

Select the first trimming entity, near the intersection
with the first entity.

Select the second trimming entity in the same manner.

The 2-D intersection is computed and if an intersection
exists, the first entity selected is trimmed or extended 
on both sides of the selected intersection(s). The
designated portion of the selected entity remains.

When one or both of the trimming entities do not actually
intersect the entity to double trim, but a projected
intersection is found, the entity is extended to meet the
trimming entity.
 
If the trimming or extending is not correct, press 
(Alt)-(I), or click on Undo in the break area to erase 
the trim or extension.


