About a century ago, August Mbius made the discovery that, if you take a strip of paper

About a century ago, August Möbius made the discovery that, if you take a strip of paper (see Figure 9.19), give it a single half-twist, and paste the ends together, you will have a piece of paper with only one side! Construct a Möbius strip, and verify that it has only one side. How many edges does it have?

Figure 9.19