Pi

In the book we mention that you can enter math formulas into the Google Search box. But if you're looking for the radius of a circle, here's a neat trick Google posted about on Pi day:

When you're using Google's calculator, use the word "pi" in the search bar to do your calculation. Say that you're measuring a tree and you want to know the radius. If you know that the circumference of the tree is 12 feet, then you can calculate the radius by entering in the equation 12/(2*pi) into Google. On the calculator, you'll see the result is 1.9098593171 and that's the radius.