You can change the length of entities or the included angle of arcs. The results are similar to extending and trimming.
This command does not affect the closed entities.
Use any of the following methods to change the length of an entity:
Dynamically drag the endpoint or angle.
Specify an incremental length or angle measured from an endpoint.
Specify the new length as a percentage of the total length or angle.
Specify a new length or included angle.
You can change the length of arcs, lines, open polylines, ellipse arc and open spline.
To change the length of an object by dragging
Choose Modify > Lengthen.
On the command line, type dynamic.
Select the object you want to change.
Specify the new endpoint or included angle.
Command line LENGTHEN
Select the object (A), and then select the new endpoint (B)
LENGTHEN: Changes the length of objects and the included angle of arcs
PEDIT: Edits polylines and three-dimensional polygon meshes
PROPERTIES: Controls properties of existing objects
SCALE: Enlarges or reduces selected objects proportionally in the X, Y, and Z directions
SPLINEDIT: Edits a spline or spline-fit polyline
STRETCH: Moves or stretches objects
System Variables Reference