visit all video for batter understanding. it may be possible they say same point because these video make by different teachers. but please visit first video of every thm
visit the following link you understand everything very well
these are some good videos
green thm
https://youtu.be/1w2f29d0VHQ
https://youtu.be/6fJE3vvjB8o
https://youtu.be/lh9dwW...