I came up with the idea to develop this lesson about two and a half years ago, in July of 1998. But it was not until November of 2000 when I finally started to work on it.

One day as I was about to start, I went to a nearby park. To my surprise, I found this small stone which, except for the round corners, had the exact shape of a right triangle:

I was simply amazed. I couldn't believe that I had found such a perfect right triangle just as I was starting to work on this lesson. The word that came to mind was predestined. It was predestined that I work on this. It was an inescapable situation. And here it is. I hope that you enjoy this lesson.