uploads/175428/JOIN_THE_LINES_01.dwg
 
Ardyman, this is not difficult, it's basic geometry.
Tell us if it's a homework or ...
 
 

Brute-force method:
 
Draw a Circle whose center is at the upper right and whose radius is defined by point A, and another whose center is at the lower left and whose radius is defined by point B.  Select the Polyline and drag the grips at points A and B to the nearer intersection of those two Circles.  Erase the Circles.
 
If you want the resulting Polyline to be closed (in entity-data terms, not just visually), use Pedit and its Edit Vertex option to Break off one of the end segments, move the other end only to that intersection of Circles, and then have the Polyline closed in the Properties box, which will put back the segment you Broke off but adjusted appropriately.
 
It could probably also be done with an AutoLISP Routine that would require only selecting the Polyline, if the same kind of situation arises often enough.

use the move command

[QUOTE=dilibere]use the move command[/QUOTE]That wouldn't work in this case.Moving either line would mean the opposite end would no longer be in the proper position.

John Connor2014-06-24 19:25:47

[... I should have said select the Lines that have A and B on their ends, if that's what they are, rather than the Polyline ....]

hello guys,its not so easy for me to do so..connecting those two ends without changing its dimension but all i have to do is to rotate the two lines using their axis. rotating used reference, repeating the command until they met. tnx..
agguloy2014-06-27 03:38:47

Hello agguloy, you have AutoCAD 2012 full so that you can use the ALIGN command for this with the help of the circles drawn in my file loaded previously : JOIN_THE_LINES_01.dwg

Hi Kent Cooper, I agree your reply.