This website show the backspin of the ball to shoot the hoop, in the free throw line you need to shoot perfect in the hoop, the arm need to be an angle to shoot the hoop nice and easy. If someone do a backspin the ball can hit the rim or the backboard. The more angle the more hoops you can get in. There is a magic formula that tells about the backspin.
This helps me because in a free throw line you can shoot the hoop without any defense men and it important so your team can get point, by doing that you need math to see the meters and how can you do it. The backspin is very good for free throw because it 
shoot better and get more shots in. When you always shoot make sure you always hit the backboard because when you hit the backboard it lets the ball to force in the hoop.