Dimostrazione is considered one of the character traits that made Leonardo da Vinci one of the most influential geniuses in history. It is one approach to problem solving.
It means a commitment to test knowledge through, experience, persistence, and a willingness to learn from mistakes. Some might call it "trial and error" and consider it a poor way to solve a problem.
Clipping is a handy way to collect important slides you want to go back to later.