The way you would put it to a nine-year-old is to say, "If a meteorite was coming to hit the Earth, how would you figure out if it was going to or not?" And if he says, "Well, what? how?" you say, "There's a magic word. It's called the tangent of an angle," and leave him alone. He'll figure it out.
Pentru un copil de nouă ani, problema ar trebui pusă astfel: „Dacă un meteorit e pe cale de a lovi Pământul, cum ai putea afla dacă o va face sau nu?” Dacă întreabă: „Ce? Cum?”, îi spui: „Cuvintele magice sunt: tangenta unui unghi” și îl lași singur. Va afla el.