I’ve had some fun playing around with old CDs and CD cases recently.

In addition to demonstrating Cavalieri’s principle both with discs and their cases, I’ve found some other mathematical uses for these objects.

Here I’ve used a stack of cases to demonstrate the difference between some geometric solids.

On the left, we have a right rectangular prism. Give that prism a slight push in a direction perpendicular to a side and you get an oblique rectangular prism.

And if you give that original prism a push along a diagonal of the base, you’ll get one of my favorite geometric objects, a parallelepiped. It may not be the perfect parallelepiped, but I’ll take it!

**Related Posts**

- The Perfect Parallelepiped
- CD Packing Problems
- CDs and Cavalieri’s Principle
- CDs and Cavalieri’s Principle: Part 2

I was hoping I could expand the picture enough to read the labels. Maybe math-lovers have the same taste in music? Haha, but great post regardless.

You can make out some of the titles in this image.

I already received a thumbs-up for the Black Sabbath album.