shown in the first video if line l and m meets  furter then why angles are equal???

 i guess you have some misunderstanding.... in da 1st video.....total 3 figures r shown.......

in dA 1st 1.... da lines are not parallel..... its jus to xplain wat r correspnding angles

in da 2nd 1.....  l an m wont meet..... de r paralel

in da 3rd 1... l and m r not parallel... actually n and p r parallel! 

hope dis hlps u 

:D