Watch the video below. Pause it whenever you need to think about what you're seeing.

This shows that pi can be thought of as a length. If you unroll the edge of a circle with diameter 1, the length of that edge is around 3.14159.  We call that edge the circumference.

Let's do something similar in Sketchpad. Download the file "What is pi.gsp" below.  Follow the directions to calculate pi.

This activity shows us that pi is a ratio.  It's a comparison of the circumference of a circle to its diameter .

Now we're going to do something similar in Sketchpad.  Download the file Circle Area below.  Follow the instructions to create a rectangle with the same area as a circle.