Safety Knights

Good one! I see this one taught (slightly) incorrectly so often. Some people look at "X" as in what's labeled on your picture (the length of the ladder), whereas others consider "X" to be the height of the building/platform the ladder is up against. It may only be a slight difference, but it can result in different answers based on how you do your calculations, which may not put you at the proper 75° angle.